Electrophysiology and noise analysis of K+-depolarized epithelia of frog skin.
Epithelia of frog skin bathed either symmetrically with a sulfate-Ringer solution or bathed asymmetrically and depolarized with a 112 mM K+ basolateral solution (Kb+) were studied with intracellular microelectrode techniques. Kb+ depolarization caused an initial decrease of the short-circuit current (Isc) with a subsequent return of the Isc toward control values in 60-90 min. Whereas basolateral membrane resistance (Rb) and voltage were decreased markedly by high [Kb+], apical membrane electrical resistance (Ra) was decreased also. After 60 min, intracellular voltage averaged -27.3 mV, transcellular fractional resistance (fRa) was 86.8%, and Ra and Rb were decreased to 36.1 and 13.0%, of their control values, respectively. Amiloride-induced noise analysis of the apical membrane Na+ channels revealed that Na+ channel density was increased approximately 72% while single-channel Na+ current was decreased to 39.9% of control, roughly proportional to the decrease of apical membrane voltage (34.0% of control). In control and Kb+-depolarized epithelia, the Na+ channel density exhibited a phenomenon of autoregulation. Inhibition of Na+ entry (by amiloride) caused large increases of Na+ channel density toward saturating values of approximately 520 X 10(6) channels/cm2 in Kb+-depolarized tissues.
Tang
J
J
Abramcheck
F J
FJ
Van Driessche
W
W
Helman
S I
SI
D000584:Amiloride / Q000494:pharmacology; D000818:Animals; D004553:Electric Conductivity; D004560:Electricity; D004594:Electrophysiology; D004848:Epithelium / Q000502:physiology; D007473:Ion Channels / Q000187:drug effects; D011188:Potassium / Q000494:pharmacology*; D011894:Rana pipiens; D012879:Skin Physiological Phenomena; D012964:Sodium / Q000378:metabolism
D007473:Ion Channels; D000584:Amiloride; D012964:Sodium; D011188:Potassium