Myocardial protection by isoflurane preconditioning preserves Ca2+ cycling proteins independent of sarcolemmal and mitochondrial KATP channels

Abstract

Introduction: Anesthetic preconditioning (APC) with volatile anesthetics improves recovery of contractile function and reduces calcium overload after ischemia/reperfusion (I/R). Mitochondrial and sarcolemmal K(ATP) channel openings have been implicated in APC-induced cardioprotection. In this study, we investigated the effect of APC on major calcium cycling proteins and its relation to K(ATP) channels.

Methods: Isolated perfused rat hearts were divided into seven groups: Time control (n = 10), ischemia control (n = 8), APC (n = 8), Mitochondrial K(ATP) inhibitor 5-hydroxydecanoate (5-HD, 200 microM, n = 8), Sarcolemmal K(ATP) inhibitor HMR1098 (HMR, 20 microM, n = 8), and APC plus 5-HD or APC plus HMR1098 (n = 8 each). APC was initiated by administering 1.5% isoflurane for 15 min, followed by a 15 min washout before 30 min of myocardial ischemia and 60 min of reperfusion. Ca2+-release channels (RyR2), Ca2+-adenosine triphosphatase (SERCA2a), phospholamban, plasma membrane Ca2+ ATPase, and sodium-calcium exchanger in the homogenate were determined by Western blot assay.

Results: APC improved contractile recovery (left ventricular developed pressure, +dP/dt, -dP/dt) after I/R, which was blocked by 5-HD and HMR. I/R depressed the density of RyR2, SERCA2a, and phospholamban, with no changes in the density of plasma membrane Ca2+ ATPase and sodium-calcium exchanger. APC reversed I/R-induced degradation of RyR2 and SERCA2a in the presence or absence of 5HD and HMR.

Conclusions: I/R-induced depression in cardiac performance is associated with a down-regulation of the major sarcoplasmic reticulum Ca2+-cycling proteins. Anesthesia preconditioning with isoflurane prevents I/R-related degradation of the RyR2 and SERCA2a in the sarcoplasmic reticulum. However, this effect was independent of its activation of K(ATP) channels.