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Can J Physiol Pharmacol. 2013 Sep;91(9):686-92. doi: 10.1139/cjpp-2012-0408. Epub 2013 Mar 5.

Involvement of the phosphatidylinositol kinase pathway in augmentation of ATP-sensitive K(+) channel currents by hypo-osmotic stress in rat ventricular myocytes.

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1
Department of Cardiovascular Medicine, Hokkaido University Graduate School of Medicine, Kita-15, Nishi-7, Kita-ku, Sapporo 060-8638, Japan.

Abstract

The objective of this study was to investigate the mechanisms of increase in the efficacy of ATP-sensitive K(+) channel (KATP) openings by hypo-osmotic stress. The whole-cell KATP currents (IK,ATP) stimulated by 100 μmol/L pinacidil, a K(+) channel opening drug, were significantly augmented during hypo-osmotic stress (189 mOsmol/L) compared with normal conditions (303 mOsmol/L). The EC50 and Emax value for pinacidil-activated IK,ATP (measured at 0 mV) was 154 μmol/L and 844 pA, respectively, in normal solution and 16.6 μmol/L and 1266 pA, respectively, in hypo-osmotic solution. Augmentation of IK,ATP during hypo-osmotic stress was attenuated by wortmannin (50 μmol/L), an inhibitor of phosphatidylinositol 3- and 4-kinases, but not by (i) phalloidin (30 μmol/L), an actin filament stabilizer, (ii) the absence of Ca(2+) from the internal and external solutions, and (iii) the presence of creatine phosphate (3 mmol/L), which affects creatine kinase regulation of the KATP channels. In the single-channel recordings, an inside-out patch was made after approximately 5 min exposure of the myocyte to hypo-osmotic solution. However, the IC50 value for ATP under such conditions was not different from that obtained in normal osmotic solution. In conclusion, hypo-osmotic stress could augment cardiac IK,ATP through intracellular mechanisms involving the phosphatidylinositol kinase pathway.

PMID:
23984989
DOI:
10.1139/cjpp-2012-0408
[Indexed for MEDLINE]

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