Prolactin, an activator of epithelial Na+ channel, inhibits basolateral K+ channels in adult tree frog skin.
Adult amphibian skin actively transports Na+ from its apical to basolateral side while in turn, K+ is recycled through Na+, K+-ATPase and K+ channels located in the basolateral membrane. We previously found that PRL stimulates Na+ transport in the skin of the adult tree frog (Hyla arborea japonica) via an increase in the open-channel density of the epithelial Na+ channel (ENaC). If PRL also activates basolateral K+ channels, this activation would help to stimulate Na+ transport, too. Whether PRL does indeed stimulate basolateral K+ channels in the adult tree frog was examined by measuring the short-circuit current across nystatin-treated skin. Both tolbutamide, a K(ATP) channel blocker, and tetrapentylammonium (TPA), a KCa channel blocker, blocked the current, the effect of TPA being more powerful than that of tolbutamide. Contrary to expectation, PRL inhibited the basolateral K+ channels in this skin. In the presence of basolateral amiloride, PRL still inhibited the basolateral K+ current, suggesting that the (Na+)-H+ exchanger located in the basolateral membrane does not mediate the inhibitory effect of PRL on the basolateral K+ channels in Hyla.
Takada
Makoto
M
Department of Physiology, Saitama Medical School, Moroyama, Iruma-gun, Saitama 650-0495, Japan. makokam@saitama-med.ac.jp
D000704:Analysis of Variance; D000818:Animals; D001001:Anura / Q000378:metabolism*; D001693:Biological Transport, Active / Q000187:drug effects; D004848:Epithelium / Q000378:metabolism; D017136:Ion Transport / Q000187:drug effects; D007564:Japan; D018408:Patch-Clamp Techniques; D011188:Potassium / Q000378:metabolism*; D026902:Potassium Channel Blockers / Q000378:metabolism / Q000494:pharmacology*; D011388:Prolactin / Q000378:metabolism / Q000494:pharmacology*; D000644:Quaternary Ammonium Compounds / Q000494:pharmacology; D012867:Skin / Q000378:metabolism*; D014044:Tolbutamide / Q000494:pharmacology
D026902:Potassium Channel Blockers; D000644:Quaternary Ammonium Compounds; D011388:Prolactin; D014044:Tolbutamide; C027435:tetrapentylammonium; D011188:Potassium