Reciprocal effects of Ca2+ and Mg-ATP on the 'run-down' of the K+ channels in opossum kidney cells.
Using the patch clamp technique, we identified an inwardly rectifying K+ channel in the membrane of opossum kidney cells. The single channel conductance was about 90 pS for inward currents and 30 pS for outward currents under a symmetrical high-K+ condition. The activity of the channel was found to decrease with time during recording from inside-out patches. In the solution with submicromolar Ca2+, the activity disappeared within 4-20 min. Intracellular Ca2+ promoted the run-down of the channel activity at 0.1-1 mM, whereas millimolar Mg-ATP restored the activity after run-down. The run-down channels could never be reactivated by ATP in the absence of Mg2+, or by a nonhydrolyzable ATP analog, AMPPNP, even in the presence of Mg2+.
Ohno-Shosaku
T
T
Department of Physiology, Osaka Medical College, Japan.
Kubota
T
T
Yamaguchi
J
J
Fukase
M
M
Fujita
T
T
Fujimoto
M
M
D000255:Adenosine Triphosphate / Q000502:physiology*; D000818:Animals; D002118:Calcium / Q000502:physiology*; D004594:Electrophysiology; D066298:In Vitro Techniques; D007668:Kidney / Q000378:metabolism* / Q000502:physiology; D009893:Opossums / Q000378:metabolism* / Q000502:physiology; D015221:Potassium Channels / Q000378:metabolism*
D015221:Potassium Channels; D000255:Adenosine Triphosphate; D002118:Calcium