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Delayed cardioprotection afforded by the glycogen synthase kinase 3 inhibitor SB-216763 occurs via a K_ATP- and MPTP-dependent mechanism at reperfusion

¹Department of Pharmacology and Toxicology, Medical College of Wisconsin; and ²Transitional Year Residency Program, Saint Joseph's Medical Center, Milwaukee, Wisconsin

Submitted 29 November 2007 ; accepted in final form 22 January 2008

Previous studies in our laboratory suggest that an acute inhibition of glycogen synthase kinase 3 (GSK3) by SB-216763 (SB21) is cardioprotective when administered just before reperfusion. However, it is unknown whether the GSK inhibitor SB21 administered 24 h before ischemia is cardioprotective and whether the mechanism involves ATP-sensitive potassium (K_ATP) channels and the mitochondrial permeability transition pore (MPTP). Male Sprague-Dawley rats were administered the GSK inhibitor SB21 (0.6 mg/kg) or vehicle 24 h before ischemia. Subsequently, the rats were acutely anesthetized with Inactin and underwent 30 min of ischemia and 2 h of reperfusion followed by infarct size determination. Subsets of rats received either the sarcolemmal K_ATP channel blocker HMR-1098 (6 mg/kg), the mitochondrial K_ATP channel blocker 5-hydroxydecanoic acid (5-HD; 10 mg/kg), or the MPTP opener atractyloside (5 mg/kg) either 5 min before SB21 administration or 5 min before reperfusion 24 h later. The infarct size was reduced in SB21 compared with vehicle (44 ± 2% vs. 61 ± 2%, respectively; P < 0.01). 5-HD administered either before SB21 treatment or 5 min before reperfusion the following day abrogated SB21-induced protection (54 ± 4% and 61 ± 2%, respectively). HMR-1098 did not affect the SB21-induced infarct size reduction when administered before the SB21 treatment (43 ± 1%); however, HMR-1098 partially abrogated the SB21-induced infarct size reduction when administered just before reperfusion 24 h later (52 ± 1%). The MPTP opening either before SB21 administration or 5 min before reperfusion abrogated the infarct size reduction produced by SB21 (61 ± 2% and 62 ± 2%, respectively). Hence, GSK inhibition reduces infarct size when given 24 h before the administration via the opening K_ATP channels and MPTP closure.

ATP-sensitive potassium channel; mitochondrial permeability transition pore; infarct size

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