Ouabain, acetazolamide, and Cl-flux in isolated frog skin: evidence for two distinct active Cl-transport mechanisms

Two distinctly different mechanisms for active Cl- transport in epithelia may exist: one, ouabain-sensitive and cation-dependent, and the other, acetazolamide-sensitive and cation-independent. As a test of this hypothesis the three active Cl- transport systems in isolated short-circuited skin of Ran...

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Bibliographic Details
Published inThe American journal of physiology Vol. 232; no. 6; p. F550
Main Authors Watlington, C O, Jessee, S D, Baldwin, G
Format Journal Article
LanguageEnglish
Published United States 01.06.1977
Subjects
Acetazolamide - pharmacology
Animals
Anura
Biological Transport, Active - drug effects
Cations, Monovalent
Chlorides - metabolism
Female
In Vitro Techniques
Isoproterenol - pharmacology
Male
Membrane Potentials
Ouabain - pharmacology
Rana pipiens
Seasons
Skin - metabolism
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Summary:Two distinctly different mechanisms for active Cl- transport in epithelia may exist: one, ouabain-sensitive and cation-dependent, and the other, acetazolamide-sensitive and cation-independent. As a test of this hypothesis the three active Cl- transport systems in isolated short-circuited skin of Rana pipiens were examined. Sensitivity to ouabain (10(-4) M) and acetazolamide (5 X 10(-3) M) and dependence on Na+ and K+ in the medium were ascertained. The first system, net chloride influx in ordinary Ringer, exhibited specific ouabain sensitivity and acetazolamide insensitivity. As we have previously shown this system to be clearly dependent on Na+ on the cis and K+ on the trans side, cation dependence was not re-studied. The second system, isoproterenol-stimulated net Cl- outflux, was also ouabain-sensitive and acetazolamide-insensitive. It was dependent on the presence of Na+ on the cis side, but the K+ dependence was less clear. In contrast to the first two, the third system (net influx in low Cl- medium sulfate Ringer containing 2.4 mM Cl-) was largely ouabain-insensitive, completely acetazolamide-sensitive and independent of both Na+ and K+. Thus, the hypothesis of two distinct mechanisms seems to hold for the three active Cl- transport systems in frog skin. Data from various other Cl- transporting epithelia are examined, and the general applicability of such a scheme of categorization for active Cl- transport mechanisms is discussed.
ISSN:0002-9513