Experimental hyperlipidemia prevents the protective effect of ischemic preconditioning on the contractility and responsiveness to phenylephrine of rat-isolated stunned papillary muscle

This study was designed to establish a hyperlipidemic diet (significant inc rease in the cholesterol and triglycerides blood levels, but without athero genic changes in heart muscle and coronary vessels) and to investigate the influence of experimental hyperlipidemia on the effects of ischemic precond itioning (PC) of rat-isolated papillary muscle on the time course of contra ctility during simulated ischemia and reperfusion and responsiveness to phe nylephrine under such a condition. The animals were divided in four experim ental groups: standard diet-fed control group (SD), SD underwent ischemic p reconditioning (SD-PC), hyperlipidemic diet-fed group (HLD) and HLD underve nt PC (HLD-PC). Force of contraction (Fc), velocity of contraction (+dF/dt) , and velocity of relaxation (-dF/dt) were measured. HLD preparations were more sensitive to ischemia then SD ones. PC, performed by 5-min perfusion w ith no-substrate solution gassing with 95% N-2/5% CO2 in the presence of fa st electrical stimulation, and 10 min of reperfusion with normal solution a nd rate of stimulation, significantly increased the resistence of isolated cardiac tissues to simulated ischemia in SD-PC group, but not in HLD-PC gro up. Negative inotropic action of phenylephrine occured in SD group of prepa rations after simulated-ischemia/reperfusion period was also prevented by P C. Therefore, we conclude that experimental hyperlipidemia significantly in fluenced the function of rat heart muscle including the higher sensitivity to ischemia and different reaction to the same PC procedure. (C) 1999 Elsev ier Science Inc. All rights reserved.