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KMID : 0811719990030030293
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Korean Journal of Physiology & Pharmacology
1999 Volume.3 No. 3 p.293 ~ p.305
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Opening of ATP-sensitive K+ Channel by Pinacidil Requires Serine/ Threonine Phosphorylation in Rat Ventricular Myocytes
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Yong-Geun Kwak Soo-Wan Chae
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Abstract
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The influences of specific protein phosphatase and protein kinase inhibitors on the ATP-sensitive K+(KATP) channel-opening effect of pinacidil were investigated in single rat ventricular myocytes using patch clamp technique. In cell-attached patches, pinacidil (100μM) induced the opening of the KATP channel, which was blocked by the pretreatment with H-7 (100μM) whereas enhanced by the pretreatment with genistein (30μM) or tyrphostin A23 (10μM). In inside-out patches, pinacidil (10μM) activated the KATP channels in the presence of ATP (0.3 mM) or AMP-PNP (0.3 mM) and in a partial rundown state. The effect of pinacidil (10μM) was not affected by the pretreatment with protein tyrosine phosphatase 1B (PTP1B,10μgml?1), but blocked by the pretreatment of protein phosphatase 2A (PP2A,1Uml?1). In addition, pinacidil (10μM) could not induce the opening of the reactivated KATP channels in the presence of H-7 (100μM) but enhanced it in the presence of ATP (1 mM) and genistein (30μM). These results indicate that the KATP channel-opening effect of pinacidil is not mediated via phosphorylation of KATP channel protein or associated protein, although it still requires the phosphorylation of serine/threonine residues as a prerequisite condition.
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