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1.
Mario Díaz Antonio Lorenzo 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1992,162(2):189-196
Summary Bioelectrical parameters and unidirectional sodium and chloride fluxes were measured under voltageclamp conditions in groups of lizards submitted to single or chronic aldosterone treatment. Both acute (AT) and chronic (CT) treatment induced significant increases in the short-circuit current (I
sc), as well as in the mucosa-to-serosa (J
m-s
Na
) and net sodium flux (J
net
Na
). In AT tissues, aldosterone did not change net chloride flux (J
net
Cl
) but did so in CT tissues. Amiloride reduced the aldosterone-increased I
sc in AT and CT tissues, inhibited J
net
Na
in AT tissues and abolished it in CT colons. J
net
Cl
was also reduced by the diuretic in the group of AT colons, whereas no changes were observed in the CT tissues. Addition of luminal DIDS reduced Na+ absorption and totally inhibited Cl- absorption in the AT tissues, but did not change I
sc. However, in CT tissues neither Na+ nor Cl- transport were affected by DIDS. A good relationship between I
sc and J
m-s
Na
was apparent after DIDS treatment in AT tissues. In this group, simultaneous addition of DIDS and amiloride totally abolished J
net
Na
and reduced I
sc to untreated control values. Addition of serosal ouabain abolished I
sc and Na+ absorption in AT and CT colons, but Cl- absorption was only altered in AT tissues. These results support the hypothesis that aldosterone induces an electrogenic, amiloride-sensitive sodium absorption, and in a dose-dependent fashion suppresses electroneutral NaCl absorption in the lizard colon.Abbreviations AT
acutely treated
- CT
chronically treated animals
- DIDS
4-4-diisothiocyanatostibene-2-2-disulfonic acid
- DMSO
dimethylsulphoxide
-
G
t
tissue conductance
-
I
sc
short circuit current
- PD
transepithelial potential difference
- SITS
4-acetamido-4-isothiocyanatostilbene-2-2-disulfonic acid
- UC
untreated controls
Preliminary results of this paper were presented at the X
th meeting of the European Intestinal Transport Group (EITG), Askov Hojskole, Denmark, 16–19 September 1990 相似文献
2.
Greg G. Goss Chris M. Wood 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1991,161(6):635-646
Summary The novel application of a two-substrate model (Florini and Vestling 1957) from enzymology to transport kinetics at the gills of freshwater trout indicated that Na+/acidic equivalent and Cl-/basic equivalent flux rates are normally limited by the availability of the internal acidic and basic counterions, as well as by external Na+ and Cl- levels. Adult rainbow trout fitted with dorsal aortic and bladder catheters were chronically infused (10–16 h) with isosmotic HCl to induce a persistent metabolic acidosis. Acid-base neutral infusions of isosmotic NaCl and non-infused controls were also performed. Results were compared to previous data on metabolic alkalosis in trout induced by either isosmotic NaHCO3 infusion or recovery from environmental hyperoxia (Goss and Wood 1990a, b). Metabolic acidosis resulted in a marked stimulation of Na+ influx, no change in Cl- influx, positive Na+ balance, negative Cl- balance, and net H+ excretion at the gills. Metabolic alkalosis caused a marked inhibition of Na+ influx and stimulation of Cl- influx, negative Na+ balance, positive Cl- balance, and net H+ uptake (=base excretion). Mean gill intracellular pH qualitatively followed extracellular pH. Classical one-substrate Michaelis-Menten analysis of kinetic data indicated that changes in Na+ and Cl- transport during acid-base disturbance are achieved by large increases and decreases in Jmax, and by increases in Km. However, one-substrate analysis considers only external substrate concentration and cannot account for transport limitations by the internal substrate. The kinetic data were fitted successfully to a two-substrate model, using extracellular acid-base data as a measure of internal HCO
3
-
and H+ availability. This analysis indicated that true Jmax values for Na+/acidic equivalent and Cl-/basic equivalent transport are 4–5 times higher than apparent Jmax values by one-substrate analysis. Flux rates are limited by the availability of the internal counterions; transport Km values for HCO
3
-
and H+ are far above their normal internal concentrations. Therefore, small changes in acid-base status will have large effects on transport rates, and on apparent Jmax values, without alterations in the number of transport sites. This system provides an automatic, negative feedback control for clearance or retention of acidic/basic equivalents when acid-base status is changing.Abbreviations Amm
total ammonia in water
- DMO
55-dimethyl-24-oxyzolidine-dione
- Jin
unidirectional inward ion movement across the gill
- Jout
unidirectional outward ion movement across the gill
- Jnet
net transfer of ions (sum of Jin and Jout) across the gill
- Jmax
maximal transport rate for ion
- Km
inverse of affinity of transporter for ion
-
PIO2
partial pressure of oxygen in inspired water
- PaCO2
partial pressure of carbon dixide in arterial blood
- TAlk
titratable alkalinity of the water
- PEG
polyethylene glycol
- NEN
New England Nuclear 相似文献
3.
D. Siebers C. Lucu K. Böttcher K. Jürss 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1994,164(1):16-22
Isolated posterior gills (no. 7) of shore crabsCarcinus maenas acclimated to brackish water of a salinity of 10 S were bathed and perfused with 50% sea water (200 mmol·l-1 Na+), and the internal perfusate collected during subsequent periods of 5 min. During a single passage through the gill the pH of the perfusion medium decreased from ca. 8.1 to ca. 7.7, a result implying that the gill possesses structures which recognize unphysiologically high pH values in the haemolymph and regulates them down to physiological values of ca. 7.7. The calculated apparent proton fluxes from the epithelial cells into the haemolymph space amounted to 17.9 mol·g fw-1·h-1, a value of only 3.8% of net Na+ fluxes observed under comparable conditions. When 0.1 mmol·l-1 KCN, an inhibitor of mitochondrial cytochrome oxidase, or 5 mmol·l-1 ouabain, a specific inhibitor of Na+/K+-ATPase were applied in the internal perfusate, down-regulation of pH was no longer observed and the gill was completely depolarized, i.e. transepithelial potential differences dropped from-7.8 to 0 mV (haemolymph space negative to bath). Regulation of pH was completely inhibited by antagonists of carbonic anhydrase (0.1 mmol·l-1 acetazolamide or 0.01 mmol·l-1 ethoxyzolamide) applied in the perfusate. Inhibitors of Na+/H+ exchange, 0.1 mmol·l-1 amiloride applied in the external bathing medium or in the internal perfusate, and symmetrical 0.01 mmol·l-1 5-(N-ethyl-N-isopropyl)amiloride, as well as inhibitors of Cl-/HCO3
- exchange and Na+/HCO3
- cotransport, 0.5 mmol·l-1 4,4-diisothiocyanatostilbene-2,2-disulphonate or 0.3 mmol·l-1 4-acetamido-4-isothiocyanatostilbene 2,2-disulphonate applied on both sides of the gill, and inhibitors of H+-ATPase, 0.05 mmol·l-1
N-ethylmaleimide and 0.1 mmol·l-1
N,N-dicyclohexylcarbodiimide —applied on both sides of the gill — did not alter the acidification of the perfusate observed in controls. Using artificial salines buffered to pH 8.1 with 0.75 mmol·l-1 tris (hydroxymethyl) aminomethane instead of 2 mmol·l-1 HCO3
-, apparent proton fluxes were reduced to 11% of controls, a result suggesting that pH regulation by crab gills needs the presence of HCO3
-. The findings obtained suggest that pH regulation by crab gills depends on the oxidative metabolism of the intact branchial epithelium and that carbonic anhydrase plays a central role in this process. Na+/H+ exchange, anion exchange or cotransport and active proton secretion seem not to be involved. While unimpaired active ion uptake is a prerequisite for pH regulation, ion transport itself is independent of it.Abbreviations acetazolamide
(N-[sulphamoyl-1, 3, 4-thiadiazol-2-yl]-acetamide)
- amiloride
3,5-diamino-6-chloropyrazinoyl-guanidine
- CA
carbonic anhydrase
- DBI
dextrane-bound inhibitor thiadiazolesulphonamide
- DCCD N
N dicyclohexylcarbodiimide
- DIDS
4,4-diisothiocyanato-stilbene-2,2-disulphonate
- EIPA
5-(N-ethyl-N-isopropyl) amiloride
- ethoxyzolamide
6-ethoxy-2-benzothiazole-sulphonamide
- fw
fresh weight
-
J
H
+
apparent proton flux
- NEM
N-ethylmaleimide
- PD
transepithelial potential difference
- PEG-STZ
polyethylene-glycol-thiadiazolesulphonamide
- STTS
4-acetamido-4-isothiocyanatostibene 2,2-disulphonate
- SW
sea water
- TRIS
tris(hydroxymethyl)aminomethane 相似文献
4.
Rachel Gabbay-Azaria Mordechay Schonfeld Shoshana Tel-Or Rachel Messinger Elisha Tel-Or 《Archives of microbiology》1992,157(2):183-190
Intracellular ion concentration and respiratory activity in the marine cyanobacterium Spirulina subsalsa was analyzed during cell transition from saline to hypersaline medium. During salt upshock, an early phase of Na+ and Cl- influx was observed, followed by an adaptation phase where both Na+ and Cl- were excluded from the cell. Respiration in intact cells was enhanced during salt upshock. S. subsalsa spheroplasts exhibited a high rate of O2 uptake, which was further enhanced in cells grown in hypersaline medium, upon addition of NaCl to the assay mixture. This effect was found to be specific to sodium ions. Plasma membrane fractions from cells grown in hypersaline medium exhibited a high rate of cytochrome oxidase activity, which was further stimulated by NaCl, and was sensitive to DCCD. Immunoblot analysis of Spirulina plasma membrane polypeptides with anti-cytochrome oxidase serum demonstrated high content of 53.4 kDa polypeptide of cytochrome oxidase, which was enriched in membranes obtained from hypersaline Spirulina cells. The enhanced respiration, and more specifically the enrichment of cytochrome oxidase activity in salt-adapted cells in situ, as well as its stimulation by NaCl in vitro and inhibition by DCCD, suggest that cytochrome oxidase is involved in the extrusion of sodium ions from cells of the salt-tolerant Spirulina subsalsa.Abbreviations DCCD
dicyclohexylcarbodiimide
- CCCP
carbonylcyanide m-chlorophenyl hydrazone
- TMPD
N, N, N, N, tetramethyl p-phenylenediamine dichloride 相似文献
5.
The relative importance of endogenous abscisic acid (ABA), as well as Na+ and Cl– in NaCl-induced responses related to growth in roots of rice seedlings were investigated. The increase in ammonium, proline and H2O2 levels, and cell wall peroxidase (POD) activity has been shown to be related to NaCl-inhibited root growth of rice seedlings. Increasing concentrations of NaCl from 50 to 150 mM progressively decreased root growth and increased both Na+ and Cl–. Treatment with NaCl in the presence of 4,4-diisothiocyano-2,2-disulfonic acid (DIDS, a nonpermeating amino-reactive disulfonic acid known to inhibit the uptake of Cl–) had less Cl– level in roots than that in the absence of DIDS, but did not affect the levels of Na+, and responses related to growth in roots. Treatment with 50 mM Na-gluconate (the anion of which is not permeable to membrane) had similar Na+ level in roots as that with 100 mM NaCl. It was found that treatment with 50 mM Na-gluconate effected growth reduction and growth-related responses in roots in the same way as 100 mM NaCl. All these results suggest that Cl– is not required for NaCl-induced responses in root of rice seedlings. Endogenous ABA level showed no increase in roots of rice seedlings exposed to 150 mM NaCl. It is unlikely that ABA is associated with NaCl-inhibited root growth of rice seedlings. 相似文献
6.
Timothy R. Traynor Scott M. O'Grady 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1992,162(1):47-53
Summary Porcine distal colon epithelium was mounted in Ussing chambers and bathed in plasma-like Ringer solution. Tissue conductances ranged from 10 to 15 mS and the short-circuit current (Isc) ranged from-15 to 220 A·cm-2. Variations in basal Isc resulted from differences in the amount of amiloride (10M mucosal addition)-sensitive Na+ absorption. Ion substitution and transepithelial flux experiments showed that 10 M amiloride produced a decrease in the mucosal-to-serosal (M-S) and net Na flux, and that this effect on Isc was independent of Cl- and HCO
3
-
replacement. When the concentration of mucosal amiloride was increased from 10 to 100 M, little change in Isc was observed. However, increasing the concentration to 1 mM produced a further inhibition, which often reversed the polarity of the Isc. The decrease in Isc due to 1 mM amiloride was dependent on both Cl- and HCO
3
-
, and was attributed to reductions in the M-S and net Na+ fluxes as well as the M-S unidirectional Cl- flux. Ion replacement experiments demonstrated that Cl- substitution reduced the M-S and net Na fluxes, while replacement of HCO
3
-
with HEPES abolished net Cl- absorption by reducing the M-S unidirectional Cl- flux. From these data it can be concluded that: (1) Na+ absorption is mediated by two distinct amiloride-sensitive transport pathways, and (2) Cl- absorption is completely HCO
3
-
-dependent (presumably mediated by Cl-/HCO
3
-
exchange) and occurs independently of Na+ absorption.Abbreviations Gt
tissue conductance
- HEPES
tris (hydroxymethyl) aminomethane
- (tris)
N-2-hydroxyethylpiperazine-N-2-ethanesulfonic acid
- Isc
short-circuit current
- Jr
residual flux
- M-S
mucosal-to-scrosal
- S-M
serosal-to-mucosal
- TTX
tetrodotoxin 相似文献
7.
N. C. Jørgensen 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1995,165(6):450-457
Simultaneous net uptake of Na+ and net extrusion of H+, both inhibited by amiloride, could be stimulated in red blood cells of the frog, Rana temporaria, either by intracellular acidification or cellular shrinkage. Net transports of Na+ and H+ were transient, dying out after 10–20 min (20°C) when stimulated by intracellular acidification but developing more slowly and proceeding for more than 60 min (20°C) when stimulated by cellular shrinkage. Evidence is presented suggesting a coupling between the transports of Na+ and H+ with an exchange ratio of 1:1 Na+/H+ exchange, stimulated by intracellular acidification, was able to readjust intracellular pH also when operating in parallel to a fully working anion exchanger in CO2/HCO
3
-
-buffered media. Inhibition of anion exchange resulted in reduced cellular net uptake of Na+.Abbreviations
DIDS
4,4-diisothiocyanatostilbene-2,2-disulphonate
-
DMSO
dimethylsulphoxide
-
IU
international unit
-
pH
e
extracellular pH
-
pH
i
intracellular pH
-
RBC
red blood cell 相似文献
8.
Horst Onken Kai Graszynski 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1989,159(1):21-28
Summary Isolated posterior gills from Chinese crabs (Eriocheir sinensis) acclimated to tap-water were perfused and bathed with full, physiological saline (containing Na+ and Cl–). Under these conditions they developed an outside positive transepithelial potential difference (PDte). Substitution of Na+ by choline on both sides of the epithelium resulted in a substantial hyperpolarization of the PDte, while substitution of Cl– by gluconate reverses PDte to outside negative values.The magnitudes of the potential differences were strongly related to the adaptation media (artificial seawater or tap-water).The KCN-sensitive, outside positive PDte was shown to be strongly dependent on Cl–. Application of thiocyanate and 4-acetamido-4-isothiocyanato-stilbene-2,2 disulfonic acid (SITS) to the bath solution resulted in a reduction of the PDte, while the Cl–-channel blocker, diphenylamine-2-carboxylic acid (DPC), showed no effect. The PDte was markedly reduced by acetazolamide, an inhibitor of carbonic anhydrase (CA), and these results are discussed with reference to the presence of a Cl–/HCO
3
–
-exchanger in the apical membrane.Chloride was shown to pass the basolateral membrane via Cl–-channels: Diphenylamine-2-carboxylic acid (DPC) reduced the PDte with an IC50 of 3.7×10–5 mol/l when added to the perfusion saline. A basolateral K+-channel and its linkage to Cl– uptake could be demonstrated by using the K+-channel blocker, Ba2+, or increased K+ concentrations in the perfusion saline (PDte decrease). Ouabain did not reduce the PDte under nominally Na+-free conditions, indicating that the Cl– transport is independent of the Na+/K+-ATPase. In this paper we shall discuss the possible energy sources and linkages between pH regulation and active Cl– absorption under these experimental conditions.Abbreviations
A9C
anthracene-9-carboxylic acid
-
CA
carbonic anhydrase
-
DMSO
dimethylsulfoxide
-
DPC
diphenylamino-2-carboxylic acid
-
PD
te
transepithelial potential difference
-
SITS
4-acetamido-4-isothiocyanato-stilbene-2,2-disulfonic acid
-
TEA
tetraethyl-ammoniumchloride 相似文献
9.
Colleen R. Talbot Daniel F. Stiffler 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1992,162(5):416-423
Summary The skin/gills and the kidneys of aquatic amphibians are potential sites of acid-base regulation. The roles of these organs in acid-base balance were examined in larval Ambystoma tigrinum following gastric infusion of ammonium salts. A single dose of 1.75 mEq NH4Cl·100 g-1 produced a mixed acidosis by 1 h after gavage. By 8 h after ingestion, pH and HCO
3
–
had increased and PCO2 had decreased as the animals recovered. A prolonged acidosis was developed in a second group by gavage of an initial dose (1.5 mEq·100 g-1), followed by periodic maintenance doses (0.25 mEq·100 g-1) to prolong the disturbance for 8 h. The magnitude of the acidosis during this period was similar to that seen at 1 h after ingestion in the time-course study. A third group of larvae were given NaCl as a control for salt loading, which induced a small but significant respiratory acidosis. Unidirectional fluxes of Na+ and Cl- were examined during these serial ingestions. Salt loading inhibited the influx of the ingested ion. Na+ influx increased during the NH4Cl-induced acidosis. A fourth group of larvae were used to partition acid and ammonia excretion between the skin and the kidneys. These animals were given (NH4)2SO4 to allow re-examination of Cl- flux rates under non-Cl--loaded conditions. The ensuing acidosis had a reduced respiratory component and, therefore, pH did not decrease as much. Cl- influx rates did decrease significantly under these conditions. In both control and acidotic conditions, the majority of the acid efflux was as ammonia and the skin was the primary site of acid excretion. However, both the skin and the kidneys increased total acid excretion, although the efflux across the skin showed a much greater increase. This suggests a primary role for the skin in acid-base regulation in aquatic amphibians.Abbreviations GFR
glomerular filtration rate
-
PO2
partial pressure of oxygen
-
PCO2
partial pressure of carbon dioxide
- SITS
4-acetamido-4-isothiocynanatostilbene-2,2-disulfonic acid
- TA
titratible acidity
Present address: Department of Organismal Biology and Anatomy, University of Chicago, 1025 E. 57th St., Chicago, IL 60637, USA 相似文献
10.
Volume-sensitive taurine transport in fish erythrocytes 总被引:5,自引:0,他引:5
Daron A. Fincham Michael W. Wolowyk James D. Young 《The Journal of membrane biology》1987,96(1):45-56
Summary Taurine plays an important role in cell volume regulation in both vertebrates and invertebrates. Erythrocytes from two euryhaline fish species, the eel (Anguilla japonica) and the starry flounder (Platichthys stellatus) were found to contain high intracellular concentrations of this amino acid ( 30 mmol per liter of cell water). Kinetic studies established that the cells possessed a saturable high-affinity Na+-dependent -amino-acid transport system which also required Cl– for activity (apparentK
m
(taurine) 75 and 80 m;V
max 0.85 and 0.29 mol/g Hb per hr for eel (20°C) and flounder cells (10°C), respectively. This -system operated with an apparent Na+/Cl–/taurine coupling ratio of 211. A reduction in extracellular osmolarity, leading to an increase in cell volume, reversibly decreased the activity of the transporter. In contrast, low medium osmolarity stimulated the activity of a Na+-independent nonsaturable transport route selective for taurine, -amino-n-butyric acid and small neutral amino acids, producing a net efflux of taurine from the cells. Neither component of taurine transport was detected in human erythrocytes. It is suggested that these functionally distinct transport routes participate in the osmotic regulation of intracellular taurine levels and hence contribute to the homeostatic regulation of cell volume. Volume-induced increases in Na+-independent taurine transport activity were suppressed by noradrenaline and 8-bromoadenosine-3, 5-cyclic monophosphate, but unaffected by the anticalmodulin drug, pimozide. 相似文献
11.
With 3-O-methylfluorescein phosphate (3-OMFP) as substrate for the phosphatase reaction catalyzed by the (Na+ + K+)-ATPase, a number of properties of that reaction differ from those with the common substratep-nitrophenyl phosphate (NPP): theK
m is 2 orders of magnitude less and the Vmax is two times greater, and dimethyl sulfoxide (Me2SO) inhibits rather than stimulates. In addition, reducing the incubation pH decreases both theK
m and Vmax for K+-activated 3-OMFP hydrolysis as well as theK
0.5 for K+ activation. However, reducing the incubation pH increases inhibition by Pi and the Vmax for 3-OMFP hydrolysis in the absence of K+. When choline chloride is varied reciprocally with NaCl to maintain the ionic strength constant, NaCl inhibits K+-activated 3-OMFP hydrolysis modestly with 10 mM KCl, but stimulates (in the range 5–30 mM NaCl) with suboptimal (0.35 mM) KCl. In the absence of K+, however, NaCl stimulates increasingly over the range 5–100 mM when the ionic strength is held constant. These observations are interpreted in terms of (a) differential effects of the ligands on enzyme conformations; (b) alternative reaction pathways in the absence of Na+, with a faster, phosphorylating pathway more readily available to 3-OMFP than to NPP; and (c) a (Na+ + K+)-phosphatase pathway, most apparent at suboptimal K+ concentrations, that is also more readily available to 3-OMFP.Abbreviations Et3N
triethyl amine
- FITC
fluorescein isothiocyanate
- HEPES
N-2-hydroxyethylpiperazine-N-2-ethanesulfonate
- MES
2-(N-morpholino)ethanesulfonate
- Me2SO
dimethyl sulfoxide
- NPP
p-nitrophenyl phosphate
- 3-OMFP
3-O-methylfluorescein phosphate
- TNP-ATP
2, (or 3)-O-(2,4,6-trinitrophenyl)-ATP 相似文献
12.
P. Pärt C. M. Wood 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1996,166(1):37-45
Using primary cultures of gill pavement cells from freshwater rainbow trout, a method is described for achieving confluent monolayers of the cells on glass coverslips. A continuous record of intracellular pH was obtained by loading the cells with the pH-sensitive flourescent dye 2,7-bis(2-carboxyethyl)-5(6)-carboxyfluorescein and mounting the coverslips in the flowthrough cuvette of a spectrofluorimeter. Experiments were performed in HEPES-buffered media nominally free of HCO3. Resting intracellular pH (7.43 at extracellular pH=7.70) was insensitive to the removal of Cl– or the application of 4-acetamido-4-isothiocyanatostilbene-2,2-disulfonic acid (0.1 mmol·l–1), but fell by about 0.3 units when Na+ was removed or in the presence of amiloride (0.2 mmol·l–1). Exposure to elevated ammonia (ammonia prepulse; 30 mmol·l–1 as NH4Cl for 6–9 min) produced an increase in intracellular pH (to about 8.1) followed by a slow decay, and washout of the pulse caused intracellular pH to fall to about 6.5. Intracellular non-HCO
3
–
buffer capacity was about 13.4 slykes. Rapid recovery of intracellular pH from intracellular acidosis induced by ammonia prepulse was inhibited more than 80% in Na+-free conditions or in the presence of amiloride (0.2 mmol·l–1). Neither bafilomycin A1 (3 mol·l–1) nor Cl removal altered the intracellular pH recovery rate. The K
m for Na+ of the intracellular pH recovery mechanism was 8.3 mmol·l–1, and the rate constant at V
max was 0.008·s–1 (equivalent to 5.60 mmol H+·l–1 cell water·min–1), which was achieved at external Na+ levels from 25 to 140 mmol·l–1. We conclude that intracellular pH in cultured gill pavement cells in HEPES-buffered, HCO
3
–
-free media, both at rest and during acidosis, is regulated by a Na+/H+ antiport and not by anion-dependent mechanisms or a vacuolar H+-ATPase.Abbreviations
BCECF
2,7-bis(2-carboxyethyl)-5(6)-carboxy-fluorescein
-
BCECF/AM
2,7-bis(2-carboxyethyl)-5(6)-carboxy-fluorescein, acetoxymethylester
-
Cholin-Cl
choline chloride
-
DMSO
dimethyl sulfoxide
-
EDTA
ethylene diamine tetra-acetic acid
-
FBS
foetal bovine serum
-
H
+
-ATPase
Proton-dependent adenosine triphosphatase
-
HEPES
N-[2-hydroxyethyl]piperazine-N[2-ethanesulfonic acid]
-
pH
i
intracellular pH
-
pH
e
extracellular pH
-
PBS
phosphate-buffered saline
-
SITS
4-acetamido-4-isothiocyanatostilbene-2,2-disulfonic acid 相似文献
13.
T. Kramer T. Michelberger H. Gürtler G. Gäbel 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1996,166(4):262-269
Investigations on the absorption of shortchain fatty acids across ruminal epithelium of sheep were performed both in vitro (Ussing chamber technique, using propionic acid representatively for shortchain fatty acids) and in vivo (washed, isolated reticulorumen). A pH-induced, nearly tenfold increase in the concentration of undissociated propionate led to an only twofold increase in mucosal-to-serosal flux of propionate (in vitro). Neither amiloride (1 mmol·l-1, in vitro) nor theophylline (10 mmol·l-1, in vivo), inhibitors of the ruminal Na+/H+ exchanger, exerted any significant influence on propionate fluxes or short-chain fatty acids absorption, respectively. Total replacement of luminal Na+ (by choline) did not alter short-chain fatty acids absorption (in vivo). Mucosal 4,4-diisothiocyanatostilbene-2,2-disulfonic acid (0.1 mmol·l-1) or mucosal nitrate (40 mmol·l-1) markedly reduced propionate net flux (in vitro). Increasing mucosal Cl- concentration brought about a significant drop in mucosal-to-serosal flux of propionate (in vitro) and in short-chain fatty acids net absorption (in vivo), respectively. The results obtained suggest that short-chain fatty acids are absorbed both as anions and as undissociated acids across ruminal epithelium of sheep. It is concluded that short-chain fatty acids anions either compete with Cl- for binding sites at a common anion-exchange mechanism or that they are absorbed by an short-chain fatty acids anion/HCO
3
-
exchanger indirectly coupled to a Cl-/HCO
3
-
exchanger via intracellular bicarbonate.Abbreviations
DIDS
4,4-diisothiocyanatostilbene-2,2-disulfonic acid
-
DMSO
dimethylsulfoxide
-
G
t
tissue conductance
-
HSCFA
protonated
- SCFA
i.e. undissociated form
-
J
ms
mucosal-to-serosal flux
-
J
sm
serosal-to-mucosal flux
-
J
net
net flux
-
I
sc
short-circuit current
-
MOPS
(3-[N-morpholino]propanesulfonic acid)
-
mu
mucosal
-
Prop
Propionate
-
SCFA
- SCFA
anions, i.e. dissociated form
-
SCFA
short-chain fatty acids
-
SEM
standard error of mean 相似文献
14.
Active Cl- uptake by Chlorella fusca was examined by using 36Cl as a label. Under light/air conditions chloride influx from a 2.4·10-5 M solution was 4.0±0.04 nmol m-2s-1. After 70±10 min a stationary 380±40 fold accumulation was reached. In dark/air and dark/argon influx and accumulation were reduced to 25±6%, respectively, 5±1.5% of the light/air control. Cl- uptake had a broad optimum around pH 7 and showed saturation kinetics with a K
M of 1.25·10-5 M and a v
max of 7.0 nmol m-2s-1 in light/air. Br- inhibited Cl- uptake strongly, J-, ClO
4
-
, SO
4
2-
, and NO
3
-
had no inhibitory effect. Inhibitor studies with carbonyl cyanide m-chlorophenylhydrazone and N,N-dicyclohexylcarbodiimide resulted in a good correlation between Cl- uptake and ATP level. 3-(3,4-Dichlorophenyl)-1,1-dimethylurea and darkness reduced transport activity without affecting the ATP level.The magnitudes of the pH gradient and the membrane potential across the cell membrane were determined and/or estimated under different conditions. It could be shown that in Chlorella Cl- transport cannot proceed via secondary active H+/Cl- cotransport. In addition, 2H+/Cl- cotransport seems unlikely for energetic reasons. On the basis of the results of this and the following study, a primary active ATP-driven Cl-/OH- exchange pump is proposed.Abbreviations CCCP
carbonyl cyanide m-chlorophenylhyd razone
- DCCD
N,N-dicyclohexylcarbodiimide
- DCMU
3-(3.4-dichlorophenyl)-1.1-dimethylurea
- DMO
5,5-dimethyloxazolidine-2,4-dione
- Hepes
N-2-hydroxyethylpiperazine-N ethane-sulfonic acid
- POPOP
1.4-bis-2-(4-methyl-5-phenyloxazolyl)-benzene
- PPO
2.5-diphenyloxazole
To whom correspondence should be addressed 相似文献
15.
Scott C. Hartsel Sandra K. Benz Woubeshet Ayenew Jacques Bolard 《European biophysics journal : EBJ》1994,23(2):125-132
Membrane diffusion potentials induced by amphotericin B (AmB), amphotericin B methyl ester (AmE), N-fructosyl AmB (N FruAmB) and vacidin, an aromatic polyene antibiotic, in ergosterol- or cholesterol-containing egg yolk phosphatidylcholine large unilamellar vesicles (LUV), were measured in various media, in order to determine the relative selectivity of Na+, K+, Cl– and other ions in these environments. Changes in the membrane potential were followed by fluorescence changes of 3,3-dipropylthiadicarbocyanine (diS-C3-(5)). Subtle changes in intercationic selectivity were monitored by measuring biionic potentials, using the fluorescent pH sensitive probe pyranine. In all the cases studied, the intereationic selectivity of the permeability pathways induced by the four antibiotics was weak compared to that of specific biological channels, though distinct differences were noted. With AmB the selectivity appeared to be concentration dependent. Above 5 × 10–7 M, the sequence determined for sterol-free small unilamellar vesicles (SUV) and cholesterol-containing SUV and LUV, Na+ > K+ > Rb+ Cs+ > Li+ (sulfate salts), corresponded closely to Eisenman selectivity sequence number VII. At 5 × 10–7 M and below the selectivity switched from Na+ > K+ to K+ > Na +. In contrast, Li+ was the most permeant ion for AmB channels in the presence of ergosterol. The selectivity between Na+
or K+ vs. Cl– varied with the antibiotic. It was very strong with vacidin at concentrations below 5 × 10–7 M, smaller with AmB, nil with AmE and N FruAmB. The selectivities observed were antibiotic, concentration and time de pendent, which confirms the existence of different types of channels.Abbreviations AmB
amphotericin B
- AmE
amphotericin B methylester
- BLM
bilayer membranes
- DiSC3(5)
3,3-dipropylthi-acarbocyanine iodide
- DMSO
dimethylsulfoxide
- EPC
egg yolk lecithin
- FCCP
carbonyl cyanide p-trifluoro methoxyphenyl-hydrazone
- HEPES
N-(2-hydroxyethylpiperazine)-N-(2-ethanesulfonic acid)
- LUV
large unilamellar vesicles
- MOPS
3-(N-morpholino)propanesulfonic acid
- N-Fru AmB
N(1-deoxy-D-fructos-1-yl) amphotericin B
- Oxonol V1
bis(3-propyl-5-oxoisoazol-4yl)pentamethine oxonol
- SUV
small unilamellar vesicles 相似文献
16.
Crude extracts or supernatants of broken cells of Clostridium formicoaceticum reduce unbranched, branched, saturated and unsaturated carboxylates at the expense of carbon monoxide to the corresponding alcohols. The presence of viologens with redox potentials varying from E
0=-295 to-650 mV decreased the rate of propionate reduction. The more the propionate reduction was diminished the more formate was formed from carbon monoxide. The lowest propionate reduction and highest formate formation was observed with methylviologen. The carbon-carbon double bond of E-2-methyl-butenoate was only hydrogenated when a viologen was present. Formate as electron donor led only in the presence of viologens to the formation of propanol from propionate. The reduction of propionate at the expense of a reduced viologen can be followed in cuvettes. With respect to propionate Michaelis Menten behavior was observed. Experiments are described which lead to the assumption that the carboxylates are reduced in a non-activated form. That would be new type of biological reduction.Non-standard abbreviations glc
Gas liquid chromatography
- HPLC
high performance liquid chromatography
- RP
reverse phase; Mediators (the figures in parenthesis of the mediators are redox potentials E
0 in mV)
- CAV2+
carbamoylmethylviologen, 1,1-carbamoyl-4,4-dipyridinium dication (E
0=-296 mV)
- BV2+
benzylviologen, 1,1-dibenzyl-4,4-dipyridinium dication (E
0=-360 mV)
- MV
methylviologen, 1,1-dimethyl-4,4-dipyridinium-dication (E
0=-444 mV)
- DMDQ2+
dimethyldiquat, 4,4-dimethyl-2,2-dipyridino-1,1-ethylendication (E
0=-514 mV)
- TMV2+
tetramethylviologen, 1,1,4,4-tetramethyl-4,4-dipyridinium dication (E
0=-550 mV)
- PDQ2+
propyldiquat, 2,2-dipyridino-1,1-propenyl dication (E
0=-550 mV)
- DMPDQ2+
dimethylpropyldiquat, 4,4-dimethyl-2,2-dipyridino-1,1-propenyl dication (E
0=-656 mV)
- PN
productivity number=mmol product (obtained by the uptake of one pair of electrons) x (biocatalyst (dry weight) kg)-1×h-1 相似文献
17.
Light transiently depolarizes the membrane of growing leaf cells. The ionic basis for changes in cell membrane electrical potentials in response to light has been determined separately for growing epidermal and mesophyll cells of the argenteum mutant of pea (Pisum sativum L.). In mesophyll cells light induces a large, transient depolarization that depends on the external Cl– concentration, is unaffected by changes in the external Ca2+ or K+ concentration, is stimulated by K+-channel blockers tetraethylammonium (TEA+) and Ba2+, and is inhibited by 3-(3-4-dichlorophenyl)-1,1-dimethylurea (DCMU). In isolated epidermal tissue, light induces a small, transient depolarization followed by a hyperpolarization of the membrane potential. The depolarization is enhanced by increasing the external Ca2+ concentration and by addition of Ba2+, and is not sensitive to DCMU. Epidermal cells in contact with mesophyll display a depolarization resembling the response of the underlying mesophyll cells. The light-induced depolarization in mesophyll cells seems to be mediated by an increased efflux of Cl– while the membrane-potential changes in epidermal strips reflect changes in the fluxes of Ca2+ and in the activity of the proton-pumping ATPase.Abbreviations BAPTA
1,2-bis(2-aminophenoxy)ethane-N,N,N,N-tetraacetic acid
- CCCP
carbonylcyanide m-chlorophenylhydrazone
- DCMU
3-(3-4-dichlorophenyl)-1,1-dimethylurea
- LID
e
light-induced depolarization in epidermal cells
- LID
m
light-induced depolarization in mesophyll cells
- LIH
light-induced hyperpolarization
- TEA+
tetraethylammonium
Ecotrans paper #43. This research was supported by National Science Foundation grants DCB-8903744 and MCB-9220110 to E.V. 相似文献
18.
P. G. McWilliams W. T. W. Potts 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1978,126(3):277-286
Summary Measurements of the transepithelial potential (Vint-Vext) across the gills of Brown Trout,Salmo trutta, were made in solutions of a range of pH and calcium concentrations. The potential was strongly dependent on external pH, being negative in neutral solutions but positive in acid solutions. The addition of calcium to the external medium produced a positive shift in potential in all but very acid media (pH 4.0–3.5), where very little change was seen. The gill membrane appears to act as a hydrogen electrode having a very high permeability to H+ ions, and the potential behaves as a diffusion potential. The presence of calcium reduced the permeability to both H+ and Na+ ions but even at a calcium concentration of 8.0 mM/l the permeability ratio H+/Na+ was still more than 900. The transepithelial potential is shown to be diffusional in origin and is discussed in terms of the relative permeability of the gill to H+, Na+ and Cl– ions. Sodium fluxes across the gills were measured and provide the basis for a theoretical consideration of Na+, Cl– and H+ fluxes across the gills in neutral and acid solutions. The positive potential at low pH largely accounts for the increased loss of sodium from fish in these conditions. 相似文献
19.
Phaseolus vulgaris (cv. Hawkesbury Wonder) was grown over a range of NaCl concentrations (0–150 mM), and the effects on growth, ion relations and photosynthetic performance were examined. Dry and fresh weight decreased with increasing external NaCl concentration while the root/shoot ratio increased. The Cl- concentration of leaf tissue increased linearly with increasing external NaCl concentration, as did K+ concentration, although to a lesser degree. Increases in leaf Na+ concentration occurred only at the higher external NaCl concentrations (100 mM). Increases in leaf Cl- were primarily balanced by increases in K+ and Na+. X-ray microanalysis of leaf cells from salinized plants showed that Cl- concentration was high in both the cell vacuole and chloroplast-cytoplasm (250–300 mM in both compartments for the most stressed plants), indicating a lack of effective intracellular ion compartmentation in this species. Salinity had little effect on the total nitrogen and ribulose-1,5-bisphosphate (RuBP) carboxylase (EC 4.1.1.39) content per unit leaf area. Chlorophyll per unit leaf area was reduced considerably by salt stress, however. Stomatal conductance declined substantially with salt stress such that the intercellular CO2 concentration (C
i) was reduced by up to 30%. Salinization of plants was found to alter the 13C value of leaves of Phaseolus by up to 5 and this change agreed quantitatively with that predicted by the theory relating carbon-isotope fractionation to the corresponding measured intercellular CO2 concentration. Salt stress also brought about a reduction in photosynthetic CO2 fixation independent of altered diffusional limitations. The initial slope of the photosynthesis versus C
i response declined with salinity stress, indicating that the apparent in-vivo activity of RuBP carboxylase was decreased by up to 40% at high leaf Cl- concentrations. The quantum yield for net CO2 uptake was also reduced by salt stress.Abbreviations and symbols A
net CO2 assimilation rate
- C
a
ambient CO2 concentration
-
C
i
intercellular CO2 concentration
- RuBP
ribulose-1,5-bisphosphate
- 13C
ratio of 13C to 12C relative to standard limestone 相似文献
20.
Vascular smooth muscle intracellular pH is maintained by the Na+/H+ and Cl–/HCO
3
–
antiporters. The Na+/H+ exchanger is a major route of H+ extrusion in most eukaryotic cells and is present in vascular smooth muscle cells in a similar capacity. It extrudes H– into the extracellular space in exchange for Na+. The Cl–/HCO
3
–
exchanger plays an analogous role to lower the pH of vascular smooth muscle cells when increases in intracellular pH occur. Its activity has also been demonstrated in A7r5 and A10 vascular smooth muscle cells. The Na+/H+ exchanger is regulated by a number of agents which act through inositol trisphosphate/diacylglycerol, to stimulate the antiporter. Calcium-calmodulin dependent protein kinase may also activate the antiporter in vivo. Phosphorylation of the Cl–/HCO
3
–
exchanger has also been observed but its physiological role is not known. Both these antiporters exist in the plasma membrane as integral proteins with free acidic cytoplasmic termini. These regions may be important in sensing changes in intracellular pH, to which these antiporters respond.Abbreviations CaM
Calmodulin
- DCCD
Dicylohexyl-Carbodiimide
- DG
Diacylglycerol
- DIDS-4
4-Diisthiocyanostilbene-2,2-Disulfonic Acid
- IP3
Inositol Trisphosphate
- PKC
protein Kinase C
- SITS-4
4-Acetamido-4-Isothiocyanstilbene-2,2-Disulfonate
- VSMC
Vascular Smooth Muscle Cell 相似文献