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RECEPTORS AND SIGNAL TRANSDUCTION
Cardiovascular Biology Research Group, Department of Pharmacology, National University of Singapore, Singapore
Submitted 7 August 2007 ; accepted in final form 15 November 2007
The present study was aimed to investigate the regulatory effect of protein kinase C (PKC) on intracellular Ca2+ handling in hydrogen sulfide (H2S)-preconditioned cardiomyocytes and its consequent effects on ischemia challenge. Immunoblot analysis was used to assess PKC isoform translocation in the rat cardiomyocytes 20 h after NaHS (an H2S donor, 10–4 M) preconditioning (SP, 30 min). Intracellular Ca2+ was measured with a spectrofluorometric method using fura-2 ratio as an indicator. Cell length was compared before and after ischemia-reperfusion insults to indicate the extent of hypercontracture. SP motivated translocation of PKC
, PKC
, and PKC
to membrane fraction but only translocation of PKC
and PKC
was abolished by an ATP-sensitive potassium channel blocker glibenclamide. It was also found that SP significantly accelerated the decay of both electrically and caffeine-induced intracellular [Ca2+] transients, which were reversed by a selective PKC inhibitor chelerythrine. These data suggest that SP facilitated Ca2+ removal via both accelerating uptake of Ca2+ into sarcoplasmic reticulum and enhancing Ca2+ extrusion through Na+/Ca2+ exchanger in a PKC-dependent manner. Furthermore, blockade of PKC also attenuated the protective effects of SP against Ca2+ overload during ischemia and against myocyte hypercontracture at the onset of reperfusion. We demonstrate for the first time that SP activates PKC
, PKC
, and PKC
in cardiomyocytes via different signaling mechanisms. Such PKC activation, in turn, protects the heart against ischemia-reperfusion insults at least partly by ameliorating intracellular Ca2+ handling.
protein kinase C isoforms; ischemia and reperfusion; cardioprotection; ATP-sensitive potassium channel
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