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1.
Dario Cremaschi Giuliano Meyer Guido Bottà Carlo Rossetti 《The Journal of membrane biology》1987,95(3):219-228
Summary In the epithelium of rabbit gallbladder, in the nominal absence of bicarbonate, intracellular Cl– activity is about 25mm, about 4 times higher than intracellular Cl– activity at the electrochemical equilibrium. It is essentially not affected by 10–4
m acetazolamide and 10–4
m 4-acetamido-4-isothiocyanostilbene-2,2-disulfonate (SITS) even during prolonged exposures; it falls to the equilibrium value by removal of Na+ from the lumen without significant changes of the apical membrane potential difference. Both intracellular Cl– and Na+ activities are decreased by luminal treatment with 25mm SCN–; the initial rates of change are not significantly different. In addition, the initial rates of change of intracellular Cl– activity are not significantly different upon Na+ or Cl– entry block by the appropriate reduction of the concentration of either ion in the luminal solution. Luminal K+ removal or 10–5
m bumetanide do not affect intracellular Cl– and Na+ activities or Cl– influx through the apical membrane. It is concluded that in the absence of bicarbonate NaCl entry is entirely due to a Na+–Cl– symport on a single carrier which, at least under the conditions tested, does not cotransport K+. 相似文献
2.
Massaki Ando 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1985,155(3):311-317
Summary Simultaneous measurements of net ion and water fluxes were made in the stripped intestine of the seawater eel, and the relationship between Na+, K+, Cl– and water transport were examined in the presence of mucosal KCl and serosal NaCl Ringer (standard condition). When Cl– was removed from both sides of the intestine, net K+ flux from mucosa to serosa was reduced, accompanied by complete blockage of water absorption. Since it has been shown that net Cl– and water fluxes depend on K+ transport under the standard condition (Ando 1983), the interdependence of K+ and Cl– transport suggests the existence of a coupled KCl transport system, while the parallelism between the net Cl– and water fluxes suggests that water absorption is linked to the coupled KCl transport. The coupled KCl and water transport were inhibited by treatment with ouabain or with Na+-free Ringer solutions, suggesting the existence of a Na+-dependent KCl transport system and linkage of water absorption to the coupled Na+–K+–Cl– transport. Since ouabain blocked the active Na+–K+–Cl– transport almost completely, the permeability coefficients for K+ and Na+ through the paracellular shunt pathway were estimated as PK=0.076 and PNa=0.058 cm/h, and PCl was calculated as 0.005 cm/h. Although Na+-independent K+ and Cltt- fluxes were observed again in the present study, these fluxes were not inhibited by CN–, ouabain or diuretics, and evoked even after blocking the Na+–K+–Cl– transport completely with ouabain. These results indicate that the Na+-independent K+ and Cl– fluxes are distinct from the active Na+–K+–Cl– transport and are not themselves active. 相似文献
3.
The Cl–/HCO
3
–
exchange mechanism usually postulated to occur in gastric mucosa cannot account for the Na+-dependent electrogenic serosal to mucosal Cl– transport often observed. It was recently suggested that an additional Cl– transport mechanism driven by the Na+ electrochemical potential gradient may be present on the serosal side of the tissue. To verify this, we have studied Cl– transport in guinea pig gastric mucosa. Inhibiting the (Na+, K+) ATPase either by serosal addition of ouabain or by establishing K+-free mucosal and serosal conditions abolished net Cl– transport. Depolarizing the cell membrane potential with triphenylmethylphosphonium (a lipid-soluble cation), and hence reducing both the Na+ and Cl– electrochemical potential gradients, resulted in inhibition of net Cl– flux. Reduction of short-circuit current on replacing Na+ by choline in the serosal bathing solution was shown to be due to inhibition of Cl– transport. Serosal addition of diisothiocyanodisulfonic acid stilbene (an inhibitor of anion transport systems) abolished net Cl– flux but not net Na+ flux. These results are compatible with the proposed model of a Cl–/Na+ cotransport mechanism governing serosal Cl– entry into the secreting cells. We suggest that the same mechanism may well facilitate both coupled Cl–/Na+ entry and coupled HCO
3
–
/Na+ exit on the serosal side of the tissue. 相似文献
4.
Giuliano Meyer Guido Bottà Carlo Rossetti Dario Cremaschi 《The Journal of membrane biology》1990,118(2):107-120
Summary In rabbit gallbladder epithelium, a Na+/H+, Cl–/HCO
3
–
double exchange and a Na+–Cl– symport are both present, but experiments on intact tissue cannot resolve whether the two transport systems operate simultaneously. Thus, isolated apical plasma membrane vesicles were prepared. After preloading with Na+, injection into a sodium-free medium caused a stable intravesicular acidification (monitored with the acridine orange fluorescence quenching method) that was reversed by Na+ addition to the external solution. Although to a lesser extent, acidification took place also in experiments with an electric potential difference (PD) equal to 0. If a preset pH difference (pH) was imposed ([H+]in>[H+]out, PD=0), the addition of Na-gluconate to the external solution caused pH dissipation at a rate that followed saturation kinetics. Amiloride (10–4
m) reduced the pH dissipation rate. Taken together, these data indicate the presence of Na+ and H+ conductances in addition to an amiloride-sensitive, electroneutral Na+/H+ exchange.An inwardly directed [Cl–] gradient (PD=0) did not induce intravesicular acidification. Therefore, in this preparation, there was no evidence for the presence of a Cl–/OH– exchange.When both [Na+] and [Cl–] gradients (outwardly directed, PD=0) were present, fluorescence quenching reached a maximum 20–30 sec after vesicle injection and then quickly decreased. The decrease was not observed in the presence of a [Na+] gradient alone or the same [Na+] gradient with Cl– at equal concentrations at both sides. Similarly, the decrease was abolished in the presence of both Na+ and Cl– concentration gradients and hydrochlorothiazide (5×10–4
m). The decrease was not influenced by an inhibitor of Cl–/OH– exchange (10–4
m furosemide) or of Na+–K+–2Cl– symport (10–5
m bumetanide).We conclude that a Na+/H+ exchange and a Na+–Cl– symport are present and act simultaneously. This suggests that in intact tissue the Na+–Cl– symport is also likely to work in parallel with the Na+/H+ exchange and does not represent an induced homeostatic reaction of the epithelium when Na+/H+ exchange is inhibited. 相似文献
5.
C. A. Rotunno M. V. Ques-von Petery M. Cereijido 《The Journal of membrane biology》1978,42(4):331-343
Summary At low concentration (1mm) of Cl– in the outer solution, the influx of chloride through the isolated skin (J
13
Cl
) of the South American frogLeptodactylus ocellatus (L.) seems to be carried by two mechanisms: (i) a passive one that exhibits the characteristics of an exchange diffusion process, and (ii) an active penetration. Studies of the influx and efflux of chloride (J
13
Cl
andJ
31
Cl
) indicate, that the presence of a high (107mm) concentration of Cl– in the outer solution activates the translocation of this ion through the cells. Studies of the unidirectional flux of Cl– across the outer barrier (J
12
Cl
) indicate that Na+ out stimulates the penetration of Cl– at this level. Cl– out, in turn, stimulates, theJ
12
Na
, but this effect is only detected at low concentrations of Na+ out. 相似文献
6.
7.
Adam Sun Eric B. Grossman Michael Lombardi Steven C. Hebert 《The Journal of membrane biology》1991,120(1):83-94
Summary Experiments were performed usingin vitro perfused medullary thick ascending limbs of Henle (MTAL) and in suspensions of MTAL tubules isolated from mouse kidney to evaluate the effects of arginine vasopressin (AVP) on the K+ dependence of the apical, furosemide-sensitive Na+:Cl– cotransporter and on transport-related oxygen consumption (QO2). In isolated perfused MTAL segments, the rate of cell swelling induced by removing K+ from, and adding onemm ouabain to, the basolateral solution [ouabain(zero-K+)] provided an index to apical cotransporter activity and was used to evaluated the ionic requirements of the apical cotransporter in the presence and absence of AVP. In the absence of AVP cotransporter activity required Na+ and Cl–, but not K+, while in the presence of AVP the apical cotransporter required all three ions.86Rb+ uptake into MTAL tubules in suspension was significant only after exposure of tubules to AVP. Moreover,22Na+ uptake was unaffected by extracellular K+ in the absence of AVP while after AVP exposure22Na+ uptake was strictly K+-dependent. The AVP-induced coupling of K+ to the Na+:Cl– cotransporter resulted in a doubling in the rate of NaCl absorption without a parallel increase in the rate of cellular22Na+ uptake or transport-related oxygen consumption. These results indicate that arginine vasopressin alters the mode of a loop diuretic-sensitive transporter from Na+:Cl– cotransport to Na+:K+:2Cl– cotransport in the mouse MTAL with the latter providing a distinct metabolic advantage for sodium transport. A model for AVP action on NaCl absorption by the MTAL is presented and the physiological significance of the coupling of K+ to the apical Na+:Cl– cotransporter in the MTAL and of the enhanced metabolic efficiency are discussed. 相似文献
8.
Our previously published whole-cell patch-clamp studies on the cells of the intralobular (granular) ducts of the mandibular glands of male mice revealed the presence of an amiloride-sensitive Na+ conductance in the plasma membrane. In this study we demonstrate the presence also of a Cl– conductance and we show that the sizes of both conductances vary with the Cl– concentration of the fluid bathing the cytosolic surface of the plasma membrane. As the cytosolic Cl– concentration rises from 5 to 150 mmol/liter, the size of the inward Na+ current declines, the decline being half-maximal when the Cl– concentration is approximately 50 mmol/liter. In contrast, as cytosolic Cl– concentration increases, the inward Cl– current remains at a constant low level until the Cl– concentration exceeds 80 mmol/liter, when it begins to increase. Studies in which Cl– in the pipette solution was replaced by other anions indicate that the Na+ current is suppressed by intracellular Br-, Cl– and NO
3
-
but not by intracellular I-, glutamate or gluconate. Our studies also show that the Cl– conductance allows passage of Cl– and Br- equally well, I-less well, and NO
3
-
, glutamate and gluconate poorly, if at all. The findings with NO
3
-
are of particular interest because they show that suppression of the Na+ current by a high intracellular concentration of a particular anion does not depend on actual passage of that anion through the Cl– conductance. In mouse granular duct cells there is, thus, a reciprocal regulation of Na+ and Cl– conductances by the cytosolic Cl– concentration. Since the cytosolic Cl– concentration is closely correlated with cell volume in many epithelia, this reciprocal regulation of Na+ and Cl– conductances may provide a mechanism by which ductal Na+ and Cl transport rates are adjusted so as to maintain a stable cell volume.This project was supported by the National Health and Medical Research Council of Australia. We thank Professor P. Barry (University of New South Wales) for assistance with the junction potential measurements. 相似文献
9.
In intact mitochondria supplemented with succinate or -hydroxybutyrate, the rates of oxygen consumption induced by beauvericin followed the ionic selectivity pattern: Na+>Rb+, Cs+, K+, Li+.When the respiratory substrate is glutamate plus malate in the absence of phosphate, the selectivity pattern is: K+>Rb+>Cs+>Li+>Na+.When the media are supplemented with phosphate, the Na+/K+ discrimination of beauvericin is considerably modified with all the respiratory substrates, being K+>Na+ with succinate and Na+>K+ with glutamate plus malate, whereas no significant ionic selectivity differences were obtained with -hydroxybutyrate.The respiratory control induced by oligomycin in submitochondrial particles is released by beauvericin only in the presence of a nigericin-like carboxylic antibiotic and an alkali metal cation, being far more effective in K+ than in Na+.This selectivity is maintained regardless of whether NADH or succinate is used as a respiratory substrate.Release of respiratory control can also be obtained with a combination of beauvericin and NH4Cl.This information indicates that the ionic selectivity pattern obtained with beauvericin in mitochondrial membranes is an intrinsic property of the antibiotic which, however, can be significantly modified by factors such as the nature of the translocatable substrate anion or other anionic species, as well as the possible operation of a Na+/H+ antiporter existent in the membrane. 相似文献
10.
Summary Na–K–Cl cotransport stoichiometry and affinities for Na, K and Cl were determined in flounder intestine. Measurement of simultaneous NaCl and RbCl influxes resulted in ratios of 2.2 for Cl/Na and 1.8 for Cl/Rb. The effect of Na and Rb on Rb influx showed first order kinetics withK
1/2 values of 5 and 4.5mm and Hill coefficients of 0.9 and 1.2, respectively. The effect of Cl on rubidium influx showed a sigmoidal relationship withK
1/2 of 20mm and a Hill coefficient of 2.0. The effects of variations in Na and Cl concentration on short-circuit current (I
sc) were also determined. TheK
1/2 for Na was 7mm with a Hill coefficient of 0.9 and theK
1/2 for Cl was 46mm with a Hill coefficient of 1.9. Based on the simultaneous influx measurements, a cotransport stoichiometry of 1Na1K2Cl is concluded. The Hill coefficients for Cl suggest a high degree of cooperativity between Cl binding sites. Measurements of the ratio of net Na and Cl transepithelial fluxes under short-circuit conditions (using a low Na Ringer solution to minimize the passive Na flux) indicate that the Cl/Na flux ratio is approximately 21. Therefore Na recycling from serosa to mucosa does not significantly contribute to theI
sc. Addition of serosal ouabain (100 m) inhibited Rb influx, indicating that Na–K–Cl cotransport is inhibited by ouabain. This finding suggests that a feedback mechanism exists between the Na–K-ATPase on the basolateral membrane and the apical Na–K–2Cl cotransporter. 相似文献
11.
Summary The ability of liver cells to control their volume in the presence of ouabain has been studied in tissue slices that were recovering at 38°C from a period of swelling at 1°C. Morphological observations were made in conjunction with measurements of the net movements of water and ions. Extrusion of water in the presence of ouabain (2mm) was accompanied by a net loss of Na+ and Cl– and by the formation of characteristic, rounded vesicles in the peri-canalicular regions of the hepatocytes; bile canaliculi were patent. When incubation was carried out in a medium in which either NO
3
–
or SO
4
2–
replaced Cl–, ouabain-resistant water extrusion was prevented and the cytoplasmic vesicles normally found with ouabain were almost totally absent. When these slices were subsequently transferred to Cl– medium with oubain, extrusion of intracellular water was initiated and cytoplasmic vesicles reappeared. Replacement of medium Na+ by Li+ mimicked the effects of ouabain on water and ion movements and ultrastructure. In addition, the ouabain-resistant extrusion of water and Cl– was reduced and there was some diminution in the number of vesicles induced by ouabain. Furosemide (2mm) had little effect on water movement or ultrastructure in the absence of ouabain, but it slowed the net water loss and substantially reduced the formation of cytoplasmic vesicles in the presence of ouabain. The results show a close relationship between ouabain-resistant water extrusion and the formation of the cytoplasmic vesicles that are characteristic of treatment with ouabain. They further suggest that a cotransport of Na+ and Cl– forms an important part of the mechanism underlying ouabain-resistant water extrusion and, specifically, that this cotransport may take place across the membranes of the cytoplasmic vesicles. 相似文献
12.
Fabian Klaus Jörg Laufer Kamil Czarkowski Nathalie Strutz-Seebohm Guiscard Seebohm Florian Lang 《Biochemical and biophysical research communications》2009,381(3):407-411
The widely expressed chloride channel ClC-2 is stimulated by the serum and glucocorticoid inducible kinase SGK1. The SGK1-dependent regulation of several carriers involves the mammalian phosphatidylinositol-3-phosphate-5-kinase PIKfyve (PIP5K3). The present experiments explored whether SGK1-dependent regulation of ClC-2 similarly involves PIKfyve. The conductance of Xenopus oocytes is increased more than eightfold by ClC-2 expression. In ClC-2-expressing oocytes, but not in water-injected oocytes, the current was further enhanced by coexpression of either, PIKfyve or constitutively active S422DSGK1. Coexpression of the inactive SGK1 mutant K127NSGK1 did not significantly alter the current in ClC-2-expressing oocytes and abrogated the stimulation of the current by PIKfyve-coexpression. The stimulating effect of PIKfyve was abolished by replacement of the serine with alanine in the SGK1 consensus sequence (S318APIKfyve). Coexpression of S318APIKfyve significantly blunted the stimulating effect of S422DSGK1 on ClC-2-activity. In conclusion, PIKfyve is a potent stimulator of ClC-2-activity and contributes to SGK1-dependent regulation of ClC-2. 相似文献
13.
Summary Gluconate substitution for serosal Cl– reduces the transepithelial short-circuit current (I
sc) and depolarizes shortcircuited frog skins. These effects could result either from inhibition of basolateral K+ conductance, or from two actions to inhibit both apical Na+ permeability (P
Na
ap
) and basolateral pump activity. We have addressed this question by studying whole-and split-thickness frog skins. Intracellular Na+ concentration (C
Na
c
) andP
Na
ap
have been monitored by measuring the currentvoltage relationship for apical Na+ entry. This analysis was conducted by applying trains of voltage pulses, with pulse durations of 16 to 32 msec. Estimates ofP
Na
ap
) and CNa/c were not detectably dependent on pulse duration over the range 16 to 80 msec. Serosal Cl– replacement uniformly depolarized short-circuited tissues. The depolarization was associated with inhibition ofI
sc across each split skin, but only occasionally across the whole-thickness preparations. This difference may reflect the better ionic exchange between the bulk medium and the extracellular fluid in contact with the basolateral membranes, following removal of the underlying dermis in the split-skin preparations.P
Na
ap
was either unchanged or increased, and CNa/c either unchanged or reduced after the anionic replacement. These data are incompatible with the concept that serosal Cl– replacement inhibitsP
Na
ap
and Na, K-pump activity. Gluconate substutition likely reduces cell volume, triggering inhibition of the basolateral K+ channels, consistent with the data and conclusions of S.A. Lewis, A.G. Butt, M.J. Bowler, J.P. Leader and A.D.C Macknight (J. Membrane Biol.
83:119–137, 1985) for toad bladder. The resulting depolarization reduces the electrical force favoring apical Na+ entry. The volume-conductance coupling serves to conserve volume by reducing K+ solute loss. Its molecular basis remains to be identified. 相似文献
14.
Dario Cremaschi Cristina Porta Guido Bottà Giuliano Meyer 《The Journal of membrane biology》1992,129(3):221-235
Transepithelial fluid transport was measured gravimetrically in rabbit gallbladder (and net Na+ transport was calculated from it), at 27 degrees C, in HCO(3-)-free bathing media containing 10(-4) M acetazolamide. Whereas luminal 10(-4) M bumetanide or 10(-4) M 4-acetamido-4'-iso-thiocyanostilbene-2,2'-disulfonate (SITS) did not affect fluid absorption, 25 mM SCN- abolished it; hydrochlorothiazide (HCTZ) in the luminal medium reduced fluid absorption from 28.3 +/- 1.6 (n = 21) to 8.6 +/- 1.6 microliters cm-2 hr-1 (n = 10), i.e., to about 30%. This maximum effect was already obtained at 10(-3) M concentration; the apparent IC50 was about 2 x 10(-4) M. The residual fluid absorption, again insensitive to SITS, was completely inhibited by SCN- or bumetanide. Cl- influx at the luminal border of the epithelium, measured under the same conditions and corrected for the extracellular space and paracellular influx, proved insensitive to 10(-4) M bumetanide, but was slowly inhibited by 10(-3) M HCTZ, with maximum inhibition (about 54%) reached after a 10-min treatment; it subsequently rose again, in spite of the presence of HCTZ. However, if the epithelium, treated with HCTZ, was exposed to 10(-4) M bumetanide during the measuring time (45 sec), inhibition was completed and the subsequent rise of Cl- influx eliminated. Intracellular Cl- accumulation with respect to the predicted activity value at equilibrium decreased significantly upon exposure to 10(-3) M HCTZ, reached a minimum within 15-30 min of treatment, then rose again significantly at 60 min. Simultaneous exposure to HCTZ and bumetanide decreased the accumulation to a significantly larger extent as compared to HCTZ alone, already in 15 min, and impeded the subsequent rise. Intracellular K+ activity rose significantly within 30 min treatment with HCTZ; the increase proved bumetanide dependent. The results obtained show that Na(+)-Cl- symport, previously detected under control conditions, is the HCTZ-sensitive type; its inhibition elicits bumetanide-sensitive Na(+)-K(+)-2Cl- cotransport. Thus, the three forms of neutral Na(+)-Cl(-)-coupled transport so far evidenced in epithelia, Na+/H+, Cl-/HCO3- double exchange (in the presence of exogenous bicarbonate), HCTZ-sensitive Na(+)-Cl- symport and bumetanide-sensitive Na(+)-K(+)-2Cl- cotransport, are all present in the apical membrane of rabbit gallbladder. 相似文献
15.
This minireview summarizes the current state of knowledge concerning the role of Cl− in the oxygen-evolving complex (OEC) of photosystem II (PSII). The model that proposes that Cl− is a Mn ligand is discussed in light of more recent work. Studies of Cl− specificity, stoichiometry, kinetics, and retention by extrinsic polypeptides are discussed, as are the results that fail
to detect Cl− ligation to Mn and results that show a lack of a requirement for Cl− in PSII-catalyzed H2O oxidation. Mutagenesis experiments in cyanobacteria and higher plants that produce evidence for a correlation between Cl− retention and stable interactions among intrinsic and extrinsic polypeptides are summarized, and spectroscopic data on the
interaction between PSII and Cl− are discussed. Lastly, the question of the site of Cl− action in PSII is discussed in connection with the current crystal structures of the enzyme. 相似文献
16.
Toshitaka Ikehara Hisao Yamaguchi Keiko Hosokawa Akira Takahashi Hiroshi Miyamoto 《The Journal of membrane biology》1993,132(2):115-124
Summary The effects of intracellular K+ and Na+ (K+
c, Na+
c) on the Na+,K+,Cl+– cotransport pathway of HeLa cells were studied by measuring ouabain-insensitive, furosemide-sensitive Rb+ influx (JRb) at various intracellular concentrations of K+ and Na+ ([K+]c, [Na+]c). When [K+]c was increased and [Na+]c was decreased, keeping the sums of their concentrations almost constant, JRb as a function of the extracellular Rb+ or Na+ concentration ([Rb+]e, [Na+]e) was stimulated. However, the apparent K
0.5 for Rb+
e or Na+
e remained unchanged and the ratio of the apparent K
+0.5 for K+
c and the apparent K
i for Na+
c was larger than 1. When JRb was increased by hypertonicity by addition of 200 mM mannitol, the apparent maximum JRb increased without change in the apparent K
0.5 for Rb+
e. These results show that K+
c stimulates and Na+
c inhibits JRb, without change in the affinities of the pathway for Rb+
e and Na+
e. The affinity for K+
c is slightly lower than that for Na+
c. Hypertonicity enhances JRb without any change in the affinity for Rb+
e. We derived a kinetic equation for JRb with respect to K+
c and Na+
c and proposed a general and a special model of the pathway. The special model suggests that, in HeLa cells, JRb takes place when Rb+
e binds to the external K+ binding site of the pathway after the binding of K+
c to the internal regulatory site.We thank Mr. T. Masuya for technical assistance. This study was supported in part by a Grant-in-Aid for Scientific Research on Priority Areas (No. 03202136) from the Japanese Ministry of Education, Science and Culture. 相似文献
17.
Kazuhiro Kikuchi Toshiko Kikuchi Fayez K. Ghishan 《The Journal of membrane biology》1990,114(3):257-265
Summary The developmental maturation of Na+–H+ antiporter was determined using a well-validated brush-border membrane vesicles (BBMV's) technique. Na+ uptake represented transport into an osmotically sensitive intravesicular space as evidenced by an osmolality study at equilibrium. An outwardly directed pH gradient (pH inside/pH outside=5.2/7.5) significantly stimulated Na+ uptake compared with no pH gradient conditions at all age groups; however, the magnitude of stimulation was significantly different between the age groups. Moreover, the imposition of greater pH gradient across the vesicles resulted in marked stimulation of Na+ uptake which increased with advancing age. Na+ uptake represented an electroneutral process.The amiloride sensitivity of the pH-stimulated Na+ uptake was investigated using [amiloride] 10–2–10–5
m. At 10–3
m amiloride concentration, Na+ uptake under pH gradient conditions was inhibited 80, 45, and 20% in BBMV's of adolescent, weanling and suckling rats, respectively. Kinetic studies revealed aK
m for amiloride-sensitive Na+ uptake of 21.8±6.4, 24.9±10.9 and 11.8±4.17mm andV
max of 8.76±1.21, 5.38±1.16 and 1.99±0.28 nmol/mg protein/5 sec in adolescent, weanling and suckling rats, respectively. The rate of pH dissipation, as determined by the fluorescence quenching of acridine orange, was similar across membrane preparation of all age groups studied. These findings suggest for the first time the presence of an ileal brush-border membrane Na+–H+ antiporter system in all ages studied. This system exhibits changes in regard to amiloride sensitivity and kinetic parameters. 相似文献
18.
《生物化学与生物物理学报:生物膜》1997,1330(2):110-112
Basolateral membranes of Aplysia foregut epithelia contain an ATP-dependent Cl− transporter (Cl− pump). Increased activity of the Cl− pump, coupled to apical and basolateral membrane depolarization, changed the Cl− transport energetics across the apical membrane but did not change the vectorially-opposite Cl− transport energetics across the basolateral membrane. 相似文献
19.
Ramesh Vemuri Margaret E. Haberland Dora Fong Kenneth D. Philipson 《The Journal of membrane biology》1990,118(3):279-283
Summary We have previously partially purified the sarcolemmal Na+–Ca2+ exchange protein and produced rabbit polyclonal antibodies to the exchanger (Philipson, K. D., Longoni, S., Ward, R. 1988.Biochim. Biophys.Acta
945:298–306). We now describe the generation of three stable murine hybridoma lines which secrete monoclonal antibodies (MAb's) to the exchanger. These MAb's immunoprecipitate 50–75% of solubilized Na+–Ca2+ exchange activity. The MAb's appear to be reactive with native conformation-dependent expitopes on the Na+–Ca2+ exchanger since they do not react on immunoblots. An indirect method was used to identify Na+–Ca2+ exchange proteins. A column containing Na+–Ca2+ exchanger immobilized by MAb's was used to affinity purify the rabbit polyclonal antibody. The affinity-purified polyclonal antibody reacted with proteinsof, apparent molecular weights of 70, 120, and 160 kDa on immunoblots of sarcolemma. The data provide strong support for our prevous association of Na+–Ca2+ exchange with these proteins. 相似文献
20.
The long arm of chromosome 4D of wheat (Triticum aestivum L.) contains a gene (or genes) which influences the ability of wheat plants to discriminate between Na+ and K+. This discrimination most obviously affects transport from the roots to the shoots, in which less Na+ and more K+ accumulate in those plants which contain the long arm of chromosome 4D. Concentrations of Na+ and K+ in the roots, and Cl− concentrations in the roots and shoots, are not significantly affected by this trait, but Na+, K+ and Cl− contents of the grain are reduced. The trait operates over a wide range of salinities and appears to be constitutive. At
the moment it is not possible to determine accurately the effect of this trait on growth or grain yield because the aneuploid
lines which are available are much less vigorous and less fertile than their euploid parents. 相似文献