Odd behaviour of Li+ in frog skin ion transport.
1. Frog skin epithelium has basolateral K+ channels that normally define the basolateral membrane potential between 80 and 100 mV. 2. The membrane mentioned also has almost silent chloride channels and a [Na+, K+, 2Cl-] cotransport, the latter probably maintains the high Cl- in the capital (also called syncytium) cells. 3. If the K+ channels are blocked by Ba2+ (or Li+) it is possible to demonstrate potential gating of the chloride channels of the basolateral membrane. 4. When the normal K+ channels are blocked, a potential-dependent K+ conductance slowly emerges. 5. If Li+ is substituted for outside Na+ the skin shows potential oscillations of about 40 mV at a frequency of about six per hour. 6. The anion channel inhibitor Indacrinone stops these oscillations. 7. The role of Cl- and K+ channels in these oscillations is discussed. 8. The transepithelial inward transport of Li+ requires the presence of Na+ and seems to be due to exchange of cellular Li+ against inside Na+ via the basolateral Na+/H+ exchanger.
D000818:Animals; D001001:Anura; D001692:Biological Transport / Q000187:drug effects; D015220:Calcium Channels / Q000502:physiology; D004848:Epithelium / Q000378:metabolism; D007474:Ion Exchange; D008094:Lithium / Q000378:metabolism*; D008564:Membrane Potentials / Q000187:drug effects; D011188:Potassium / Q000494:pharmacology; D015221:Potassium Channels / Q000502:physiology; D012867:Skin / Q000378:metabolism*; D012964:Sodium / Q000494:pharmacology
D015220:Calcium Channels; D015221:Potassium Channels; D008094:Lithium; D012964:Sodium; D011188:Potassium