共查询到20条相似文献,搜索用时 10 毫秒
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Energetics of coupled active transport of sodium and chloride 总被引:4,自引:4,他引:0
A Clark electrode was used to measure oxygen consumption by the gall bladder, in which there is a direct and one-to-one linkage between active Na and active Cl transport. O2 uptake was reversibly depressed when Cl in the mucosal bathing solution was replaced by a poorly transported anion, such as sulfate. This effect of Cl was abolished by ouabain or in Na-free solutions. When the anion was chloride, treatment with ouabain or replacement of Na by a poorly transported cation depressed QO2 more than did replacement of Cl. However, ouabain or removal of Na also depressed QO2 in Na2SO4 solutions, in which salt transport is minimal. It is concluded that oxygen uptake in the gall bladder consists of three fractions: 9% requires both Na and Cl, is inhibited by ouabain, and is linked to the NaCl pump; 36% requires Na but not Cl, is inhibited by ouabain, and possibly is linked to the cellular K uptake mechanism; and 55% represents basal uptake. If the extra oxygen uptake observed during transport supplies all the energy for transport, then 25 Na + 25 Cl ions are transported actively per O2 consumed; i.e., twice as many ions as in epithelia which transport only Na actively. This extra uptake is more than sufficient to supply the energy for overcoming internal membrane resistance under the experimental conditions used. 相似文献
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Respiration and active sodium transport of isolated toad bladder 总被引:3,自引:0,他引:3
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The aim of the study was to evaluate the effect of hibernation on electrophysiological parameters of isolated frog skin under control incubation (Ringer solution) and after inhibition of Na+ and CI- transepithelial transport by application of amiloride and bumetanide. The transepithelial electrical potential difference (PD in mV) was measured before and after mechanical stimulation of isolated frog skin. The tissues were mounted in a modified Ussing chamber. The results revealed a reduced PD of frog skin during hibernation. In February, as compared with November, PD of frog skin incubated in Ringer solution decreased by about 50%. Hibernation also affected hyperpolarization (dPD) of frog skin after mechanical stimulation. In November and December, dPD was about 50% and 30% lower, respectively, compared with the subsequent two months of the experiment. The incubation of frog skin with amiloride, a sodium ion channel blocker, resulted in reduced values of all measured electrophysiological parameters irrespective of the phase of hibernation. After application of chloride ion transport inhibitor (bumetanide), the PD in November and December decreased compared with the control incubation by about 80% and 75%, while in January and February by about 40% and 25%, respectively. In January and February dPD increased by four times and three times as compared with November and December. Hibernation reduces net ion flow in isolated frog skin. During the initial period of hibernation the sensitivity of the skin to mechanical stimulation also decreases. Towards the end of hibernation, on the other hand, excitation of mechanosensitive ion channels takes place. 相似文献
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Sodium activation of chloride transport in the frog cornea 总被引:1,自引:0,他引:1
J A Zadunaisky 《Biochimica et biophysica acta》1972,282(1):255-257
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Summary In the isolated frog cornea, the effects of 0.1mm epinephrine were measured on both the transepithelial and intracellular electrical parameters. Epinephrine increased the short-circuit current (I
sc) and transepithelial electrical conductance (g
t) by 176 and 96%, respectively. The effective electromotive driving force for active transepithelial Cl transport (E
Cl) was 45 mV and agrees with the value forE
Cl calculated by a different technique in the isolated rabbit corneal epithelium (Klyce, S.D., Wong, R.K.S., 1977,J. Physiol. (London)
266: 777). With respect to the tear-side bathing solution, epinephrine caused the intracellular potential difference of shortcircuited frog corneas to decrease from –54 to –50 mV (P>0.05). The fractional resistance of the apical membrane {F(R
o)=(Ro/Ro+Ri)} whereR
o andR
i represent the resistances of the apical and basolateral membranes, respectively, decreased from 0.38±0.06 to 0.23±0.03. Using these values ofF(R
o) and the cellular conductances, the calculated Cl resistances ofR
o andR
i decreased 4.3- and 2.3-fold, respectively. However, the value forE
Cl calculated from the intracellular electrical measurements (48 mV) did not appear to change since this value was in close agreement with the value forE
Cl calculated from the effects of epinephrine on the transepithelial electrical parameters. Thus, the effects of epinephrine onI
sc andg
t can be accounted for by increases in the Cl conductance of both the apical and basolateral membranes. Epinephrine caused the potential difference across the basolateral membrane to hyperpolarize by 9 mV. All of these results are consistent with the notion that the steps in transepithelial Cl transport include uphill movement into the cell across the basolateral membrane followed by downhill movement across the apical membrane into the tear-side bathing solution. 相似文献
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Summary 5-hydroxytryptamine, when present in the solution bathing the inside surface of bullfrog skin at concentrations of 0.25–25.0 mM, reduced both electrical potential difference and short-circuit current across the skin. The magnitude of reduction in potential difference and short-circuit current was dependent on 5 HT concentration. Reduction in sodium influx entirely accounted for the reduction in short-circuit current. Preliminary evidence suggested a competition between 5 HT and vasopressin in the production of their effects on sodium transport across the skin, while high Ca++ concentrations and 5 HT seemed to act independently of each other.Dr. Henry C. and Bertha H. Buswell Fellow. 相似文献
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Crandall E. D.; Heming T. A.; Palombo R. L.; Goodman B. E. 《Journal of applied physiology》1986,60(1):289-294
We have previously presented evidence that cultured alveolar epithelial cell monolayers actively transport sodium from medium to substratum, and that this process can be stimulated by beta-agonists. In this study the isolated perfused rat lung was utilized to investigate sodium transport across intact mammalian alveolar epithelium. Radioisotopic tracer(s) (22Na and/or [14C]sucrose) were instilled into the airways of isolated Ringer-perfused rat lungs. The appearance of isotope(s) in the recirculated perfusate was measured and a permeability-surface area product was calculated. Pharmacological agent(s) (terbutaline and/or propranolol) were present in the instillate or were added to the perfusate during the experiments. Terbutaline alone, whether in the instillate or perfusate, caused a significant increase in 22Na flux. This increase was prevented by the presence of propranolol. [14C]sucrose fluxes were unaffected by the presence of terbutaline. These data are consistent with the presence of an active component of sodium transport across intact mammalian alveolar epithelium that leads to removal of sodium from the alveolar space. 相似文献
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Time-dependent changes in the in vitro effects of sodium chloride on photosynthetic electron transport of isolated chloroplasts 总被引:1,自引:0,他引:1
The effects of a wide concentration range of NaCl and sorbitol on three photosynthetic electron transport reactions of Pisum sativum L. cv. Feltham First chloroplasts were examined as a function of time from thylakoid membrane isolation. Rates of electron flow from water to diaminodurene (DAD) and ferricyanide were determined polarographically, whilst photoreduction of 2,6-dichlorophenolindophenol (DCPIP) was monitored spectrophotometrically. Assay of thylakoids immediately after isolation showed that the rate of photoreduction of all three electron acceptors decreased with increasing salt concentration. However, 100 min after leaf homogenisation the response pattern of ferricyanide and DCPIP photoreduction to increasing NaCl, but not increasing sorbitol concentration, became significantly modified. This was not the case for DAD photoreduction. The results are discussed in relation to the assessment of the possible effect of salinity on photosynthetic electron transport in vivo. 相似文献
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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
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G
t
tissue conductance
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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
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Fluxes of D-xylose-1-C14 (xylose) across the wall of the isolated intestine of the bullfrog were studied. When sodium was the principal cation in the mucosal bathing fluid, the transport rate of xylose from the mucosa to the serosa was about 5 times greater than the transport rate from the serosa to the mucosa, indicating an active intestinal transport for this sugar. With potassium as the principal cation on the mucosal side, the transport rate of xylose from the mucosal to the serosal compartment is reduced about 5 to 6 times without appreciable change in the serosal to mucosal transport. The asymmetry was also considerably reduced when ouabain was added to the mucosal and serosal compartments. The data confirm the in vitro and in vivo observations indicating active transport of xylose and are also in accord with the earlier findings that active transport of sugars in the intestine is dependent upon the presence of sodium ions in the mucosal compartment and is inhibited by cardioactive steroids. Since the chemical constitution of xylose does not meet the requirements which were hitherto considered necessary for active transport of sugars in the intestine, this structural requirement has to be revised. 相似文献
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Oscar A. Candia 《生物化学与生物物理学报:生物膜》1973,298(4):1011-1014
Active transport of Cl− accounts for 90% of the short-circuit current (s.c.c.) in the isolated frog cornea. 1·10−5 M furosemide produced a 50% reversible inhibition of this s.c.c. 1·10−4 M ethacrynic acid reduced the corneal s.c.c. to 32% of the control. In the isolated frog skin epithelium furosemide had no effect on the s.c. at a concentration of 1·10−4 M and a small stimulation at a concentration of 1·10−3 M. The furosemide inhibitory effects seems to be specific for Cl−, as it also inhibits Cl− transport in the ascending limb of the loop of Henle (Burg, M.B. (1972) Proc. 5th Int. Congr. Nephrol., p. 50, Abstr.). 相似文献