Differential role of calcium/calmodulin-dependent, protein kinase II in desflurane-induced preconditioning and cardioprotection by metoprolol - Metoprolol blocks desflurane-induced preconditioning

Background: Anesthetic preconditioning is mediated by beta-adrenergic signaling. This study tested the hypotheses that desflurane-induced preconditioning is dose-dependently blocked by metoprolol and mediated by calcium/calmodulin-dependent protein kinase II (CaMK II). Methods. Pentobarbital-anesthetized New Zealand White rabbits were instrumented for measurement of systemic hemodynamics; and subjected to 30 min of coronary artery occlusion followed by 3 h of reperfusion. Rabbits were assigned to receive vehicle (control), 0.2, 1.0, 1.75, or 2.5 mg/kg metoprolol for 30 min, or the CaMK H inhibitor KN-93 in the absence or presence of 1.0 minimum alveolar concentration desflurane. Protein expression of CaMK H, phospholamban, and phospho-phospholamban was measured by Western blotting. Myocardial infarct size and area at risk were measured with triphenyhetrazolium staining and patent blue, respectively. Results: Baseline hemodynamics were not different among groups. Infarct size was 60 +/- 3% in control and significantly (* P < 0.05) decreased to 33 +/- 2%* by desflurane. The CaMK H inhibitor KN-93 did not affect infarct size (55 +/- 4%) but blocked desflurane-induced preconditioning (57 +/- 3%). Metoprotol at 0.2 and 1.0 mg/kg had no effect on infarct size (55 +/- 3% and 53 +/- 3%) whereas metoprolol at 1.75 and 2.5 mg/kg reduced infarct size to 48 +/- 4%* and 39 +/- 5%*, respectively. Desflurane-induced preconditioning was attenuated by metoprolol at 0.2 mg/kg, leading to an infarct size of 46 +/- 5%*, and was completely abolished by metoprolol at 1.0, 1.75, and 2.5 mg/kg, resulting in infarct sizes of 51 +/- 3%, 52 +/- 3%, and 55 +/- 3%, respectively. Conclusions: Desflurane-induced preconditioning is dose-dependently blocked by metoprolol and mediated by CaMK II.