Forskolin activates gated Cl- channels in frog skin.
We investigated the effect of forskolin on Cl- movements across the isolated epithelium of frog skin. With Cl- on both sides, forskolin (50 mumol/l) increased the transepithelial conductance considerably and elicited significant Cl- secretion. Establishing transepithelial Cl- gradients markedly increased the Cl- currents (ICl). During forskolin treatment, the power density spectra (PDS) of the fluctuation in transepithelial current contained a Lorentzian component that depended on the presence of Cl- in the bathing solutions. Mucosal as well as serosal diphenylamine-2-carboxylic acid (DPC; 1 mmol/l) partially depressed ICl as well as the Lorentzian noise component. Microelectrode recordings from cells involved in transepithelial Na+ absorption showed that forskolin activates gated Cl- channels in a cellular pathway in parallel with the Na+-transporting granulosum cells of the frog skin. The activation of the Cl- -dependent currents and Lorentzian noise was rather variable, and adaptation of the animals to solutions that contained 40 or 60 mmol/l NaCl increased the sensitivity to forskolin. In skins of salt-adapted animals, oxytocin (0.1 U/ml) also slightly activated the Cl- pathway. On the other hand, oxytocin and 8-(4-chlorophenylthio)adenosine 3',5'-cyclic monophosphate (CPT-cAMP; 1 mmol/l) were without effect in control skins.
De Wolf
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Laboratorium voor Fysiologie, Katholieke Universiteit Leuven, Belgium.
Van Driessche
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W
Nagel
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D000818:Animals; D018118:Chloride Channels; D002712:Chlorides / Q000378:metabolism / Q000502:physiology*; D005576:Colforsin / Q000494:pharmacology*; D000242:Cyclic AMP / Q000031:analogs & derivatives / Q000494:pharmacology; D004848:Epithelium / Q000187:drug effects / Q000502:physiology; D066298:In Vitro Techniques; D007473:Ion Channels / Q000187:drug effects / Q000502:physiology*; D007700:Kinetics; D008565:Membrane Proteins / Q000502:physiology*; D010121:Oxytocin / Q000494:pharmacology; D011896:Rana temporaria; D012879:Skin Physiological Phenomena; D013873:Thionucleotides / Q000494:pharmacology; D062367:ortho-Aminobenzoates / Q000494:pharmacology
D018118:Chloride Channels; D002712:Chlorides; D007473:Ion Channels; D008565:Membrane Proteins; D013873:Thionucleotides; D062367:ortho-Aminobenzoates; D005576:Colforsin; C015929:8-((4-chlorophenyl)thio)cyclic-3',5'-AMP; D010121:Oxytocin; C001209:fenamic acid; D000242:Cyclic AMP