Effect of Adenosine and Intracellular GTP on KATP Channels of Mammalian Skeletal Muscle |
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Authors: | R. Barrett-Jolley A. Comtois N.W. Davies P.R. Stanfield N.B. Standen |
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Affiliation: | (1) Ion Channel Group, Department of Cell Physiology & Pharmacology, University of Leicester, PO Box 138, Leicester LE1 9HN, UK, GB |
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Abstract: | We investigated the action of adenosine and GTP on KATP channels, using inside-out patch clamp recordings from dissociated single fibers of rat flexor digitorum brevis (FDB) skeletal muscle. In excised patches, KATP channels could be activated by a combination of an extracellular adenosine agonist and intracellular Mg2+-ATP and GTP or GTP-γ-S. The activation required hydrolyzable ATP and could be partially reversed with Mg2+, suggesting that it may involve a G-protein dependent phosphorylation of KATP channels. We found that KATP channels of the rat FDB could not be activated by Mg2+-ATP alone or by Mg2+-ATP in the presence of extracellular adenosine. Patches whose channel activity had been `rundown' by Ca2+ could not be recovered by adenosine, GTP or Mg2+-ATP. KATP channels activated by adenosine receptor agonists had a similar ATP sensitivity to those under control conditions; but adenosine appears to be able to switch these KATP channels from an inactive to an active mode. Received: 29 December 1995/Revised: 22 March 1996 |
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Keywords: | : Potassium channel — Adenosine — Adenosine triphosphate (ATP) — Skeletal muscle |
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