Reciprocal effects of Ca2+ and Mg-ATP on the ‘run-down’ of the K+ channels in opossum kidney cells
- 21 Downloads
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+.
Key wordsPatch clamp Kidney cell K+ channel Run-down Ca2+ ATP
Unable to display preview. Download preview PDF.
- Belles B, Hescheler J, Trautwein W, Blongren K, Karlsson JO (1988) A possible physiological role of the Ca-dependent protease calpain and its inhibitor calpastatin on the Ca current in guinea pig myocytes. Pflügers Arch 412:554–556Google Scholar
- Chad JE, Eckert R (1986) An enzymatic mechanism for calcium current inactivation in dialysedHelix neurones. J Physiol 378:31–51Google Scholar
- Findlay I (1987) ATP-sensitive K+ channels in rat ventricular myocytes are blocked and inactivated by internal divalent cations. Pflügers Arch 410:313–320Google Scholar
- Giebisch G, Aronson PS (1986) The proximal nephron. In: Andreoli TE, Hoffman JF, Fanestil DD, Schults SG (eds) Physiology of membrane disorders. Plenum, New York p 669–700Google Scholar
- Hamill OP, Marty A, Neher E, Sakmann B, Sigworth FJ (1981) Improved patch-clamp techniques for high-resolution current recording from cells and cell-free membrane patches. Pflügers Arch 391:85–100Google Scholar
- Kawahara K, Hunter M, Giebisch G (1987) Potassium channels inNecturus proximal tubule. Am J Physiol 253:F488-F494Google Scholar
- Ohno-Shosaku T, Zünkler BJ, Trube G (1987) Dual effects of ATP on K+ currents of mouse pancreatic β-cells. Pflügers Arch 408:133–138Google Scholar
- Parent L, Cardinal J, Sauvé R (1988) Single-channel analysis of a K channel at basolateral membrane of rabbit proximal convoluted tubule. Am J Physiol 254:F105-F113Google Scholar
- Ubl J, Murer H, Kolb H-A (1988) Hypotonic shock evokes opening of Ca2+-activated K channels in opossum kidney cells. Pflügers Arch 412:551–553Google Scholar