Potassium dependence of sodium transport in frog skin.
22Na+ and 42K+ fluxes across the basolateral membrane of the isolated epithelium of frog skin were investigated with regard to dependence on K+ in the basolateral solution. When K+ was removed from the basolateral solution (K+-free Ringer), there was a transient rise in short circuit current (Isc) that could be eliminated by pretreatment with ouabain. Concurrently, the apparent sodium efflux across the basolateral membrane (JNa*13) showed either no change or an immediate (1-2 min) small decrease (approximately equal to 10%) that was followed by a small transient increase. K+ fluxes showed either no change or a small decrease under these conditions. JNa*13 was partially ouabain sensitive during all of the above treatments. Furosemide partially inhibited both sodium and potassium flux after K+-free treatment. The pump, as defined by ouabain sensitivity of Na+ flux, continued to work even after 20 minutes of K+-free treatment. Pump activity may be maintained by potassium leaking from the cells that is recycled by the pump. However, the ouabain-sensitive transient rise in Isc after K+-free treatment cannot readily be explained by changes in either Na+ or K+ flux. A change in pump coupling ratio provides one explanation for these data.
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Department of Physiology, Southern Illinois University, School of Medicine, Carbondale 62901.
D000818:Animals; D001693:Biological Transport, Active / Q000187:drug effects; D004553:Electric Conductivity; D005665:Furosemide / Q000494:pharmacology; D007473:Ion Channels / Q000187:drug effects / Q000378:metabolism; D008564:Membrane Potentials; D010042:Ouabain / Q000494:pharmacology; D011188:Potassium / Q000502:physiology*; D011894:Rana pipiens / Q000502:physiology*; D012867:Skin / Q000378:metabolism*; D012964:Sodium / Q000378:metabolism*
D007473:Ion Channels; D010042:Ouabain; D005665:Furosemide; D012964:Sodium; D011188:Potassium