Kinetic characterization of the chloride dependence of sodium transport in the frog skin

Ferreira, Karin T.G.; Guerreiro, Maria Margarida; Ferreira, H. G.

doi:10.1016/0005-2736(73)90418-5

Cited by 11 publications

(5 citation statements)

References 12 publications

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“…Field & Young (1973) have shown for instance that the kinetic characteristics of Na transport in the rat submaxillary main duct, a 'tight epithelium', is first order with a Ki of 29 m-molefl. Frog skin also shows first order kinetics for the transport of Na (Frazier, Dempsey & Leaf, 1962;Ferreira, Guerreiro & Ferreira, 1973;Moreno, Reisin, Boulan, Rotunno & Cereijido, 1973).…”

Section: Possible Changes In Transepithelial Potential Difference or mentioning

confidence: 99%

Kinetics of active sodium transport in rat proximal tubules and its variation by cardiac glycosides at zero net volume and ion fluxes. Evidence for a multisite sodium transport system.

Györy¹,

Lingard²

1976

The Journal of Physiology

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1. Transepithelial Na concentration difference, deltaCNa, across proximal tubules of rat kidney was measured at varying intraluminal Na concentrations (CNainfinity) under conditions of zero net volume and Na flux. Simultaneous stopped-flow intratubular and artificial peritubular capillary perfusion techniques were used together with intratubular raffinose to achieve zero net fluxes. Under these conditions in rat proximal tubules, deltaCNa represents active transport, JactNa, factored by permeability, PNa, plus an electrical factor depending on transepithelial potential difference. 2. The relationship between CNainfinity and deltaCNa appeared sigmoidal with saturation being reached when intratubular Na was above 80 m-mole/kg. In the presence of ouabain (10(-2)M) and scilliroside (10(-3)M) the relationship remained the same. The maximum deltaCNa was reduced by approximately 50% by cardiac glycoside inhibition whereas the half-saturation constant was essentially unchanged. These changes from the control represent simple non-competitive inhibition by the cardiac glycosides. 3. Absence of potential difference (p.d.) measurements precludes exact description of the relation between true active transport and substrate concentration but much evidence indicates that the apparently sigmoid relation in the presence and absence of cardiac glycoside inhibition, would be retained if correction of deltaCNa values were possible. Such results could then be explained if there are at least three or more sites for Na on the pump system, of which at least two are not cardiac glycoside sensitive. They would also unequivocally exclude the presence of a single-site single-pump system or the simple algebraic addition of two such units since the kinetic curves for both would be hyperbolic rather than sigmoidal.

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Section: Possible Changes In Transepithelial Potential Difference or mentioning

confidence: 99%

Kinetics of active sodium transport in rat proximal tubules and its variation by cardiac glycosides at zero net volume and ion fluxes. Evidence for a multisite sodium transport system.

Györy¹,

Lingard²

1976

The Journal of Physiology

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“…Several authors (Biber & Curran, 1970;Biber et al 1972;Cereijido, Herrera, Flannigan & Curran, 1964;Erlij & Smith, 1973;Moreno et al 1973) have shown that the Na uptake across the external barrier of the frog skin exhibits saturation properties and these observations may explain the saturation kinetics of the Na dependence of the Ic as described in a previous paper (Ferreira et al 1973). The I'c is also dependent on external Cl following saturation kinetics.…”

Section: Resultsmentioning

confidence: 79%

“…In a previous paper Ferreira et al (1973) suggested that the Na uptake a-cross the external barrier of the frog skin might be partially coupled to that of Cl. Since then a mechanism of that type was described by Nellans et al (1973,1974) in the mammalian small intestine and by Frizzell et al (1975) in the mammalian gall-bladder.…”

Section: Resultsmentioning

confidence: 99%

“…Several authors (Cereijido et al 1964;Biber & Curran 1970;Erlij & Smith 1973;Moreno et al 1973) have shown that the dependence of the Na uptake across the external barrier on external Na concentration exhibits saturation kinetics and this was interpreted as evidence for a carrier being involved in the Na translocation. In a previous paper it was suggested that the removal of Cl might affect this mechanism since it was shown that the external Na affinity of the short-circuit current was lower in the absence of chloride (Ferreira et al 1973). But since Cl had been removed from the solutions bathing both sides of the preparation one might be dealing with more than one mechanism.…”

Section: Discussionmentioning

confidence: 99%

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Chloride dependence of active sodium transport in frog skin: the role of intercellular spaces.

Ferreira¹,

Hill²

1978

The Journal of Physiology

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SUMMARY1. In agreement with previous observations the replacement of Cl by a nonpenetrating anion in the solution bathing either the outside or both sides of the frog skin causes a fall in the short-circuit current.2. When Cl is replaced by a non-penetrating anion in the solution bathing the outside of the frog skin the I., is still a correct measure of the net Na transport.3. Under the same conditions both active and shunt paths seem to be affected since there is a decrease in In, Na influx, amiloride-dependent conductance, and initial Na uptake across the external barrier, together with a decrease in Cl-backfluxes and amiloride-independent conductance. There is also a decrease in water permeability and a reduction in size of the intercellular spaces. 4. The removal of C1 does not appear to affect the entry step of Na but may have an effect on the shunt path. This in turn may change the active Na transport.

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“…Similar values have been found in vivo in other freshwater animals (see Maetz, 1974). With the isolated skin mounted in open-or short-circuit conditions, however, the affinity of the sodium transport system is considerably lower, the Ko.5 being between 4.0 and 20 meq (Kirschner, 1955;Gil Ferreira, Guerreiro & Gil Ferreira, 1973;Mandel & Curran, 1973;Moreno etal., 1973;Zeiske & Lindemann, 1974;Mandel, 1978). These in vitro studies were carried out at external sodium concentrations between 6 and 120 meq.…”

Section: Evidence For Two Sodium and Chloride Transport Componentsmentioning

confidence: 99%

Kinetics of ionic transport across frog skin: Two concentration-dependent processes

Ehrenfeld¹,

Garcia-Romeu²

1980

J. Membrain Biol.

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Sodium and chloride influxes across the nonshort-circuited isolated skin of Rana esculenta were measured at widely varying external ionic concentrations. The curve describing sodium transport has two Michaelis-Menten components linked at an inflection point occurring at an external sodium concentration of about 7 meq. Chloride transport can also be represented by two saturating components. A possible explanation of these kinetics is discussed. At sodium concentrations lower than 4 meq it is possible to define a component of the sodium transport mechanism as having a high affinity for sodium and which is independent of the nature of the external anion. A high affinity for chloride of the chloride transport system functioning at low external concentrations is also found but is significantly different from that of sodium. These systems show the physiological characteristics of the countertransports (Na est(+)/H int(+); Cl ext(-)/HCO 3int(-)) functioning at low external concentrations. At external concentrations higher than 4 meq a low affinity transporting system in which chloride and sodium are linked superimpose on the high affinity compoents. The physiological significance of these results is discussed.

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Kinetic characterization of the chloride dependence of sodium transport in the frog skin

Cited by 11 publications

References 12 publications

Kinetics of active sodium transport in rat proximal tubules and its variation by cardiac glycosides at zero net volume and ion fluxes. Evidence for a multisite sodium transport system.

Kinetics of active sodium transport in rat proximal tubules and its variation by cardiac glycosides at zero net volume and ion fluxes. Evidence for a multisite sodium transport system.

Chloride dependence of active sodium transport in frog skin: the role of intercellular spaces.

Kinetics of ionic transport across frog skin: Two concentration-dependent processes

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