Role of transsarcolemmal Ca2+ entry in the negative inotropic effect of nitrous oxide in isolated ferret myocardium.

Abstract

The purpose of this study was to investigate the effects of nitrous oxide (N2O) on transsarcolemmal calcium influx in isolated ferret right ventricular myocardium. Using a range of loading conditions, papillary muscles were equilibrated in 50% nitrogen (N2) or 50% N2O in oxygen in the presence and absence of ryanodine, a specific inhibitor of calcium release from the sarcoplasmic reticulum. After equilibration in 50% N2O or 50% N2 in oxygen, peak developed force, peak isotonic shortening, and maximal unloaded velocity of shortening were compared in the presence and absence of 10(-6) M ryanodine. Fifty percent N2O caused a significant reduction in contractility in control conditions and a further significant reduction in contractile variables in the presence of 10(-6) M ryanodine. We conclude that at least part of the negative inotropic effect of N2O is due to an inhibition of transsarcolemmal calcium influx.