INFLUENCE OF SEX, DIABETES AND ETHANOL ON INTRINSIC CONTRACTILE PERFORMANCE OF ISOLATED RAT MYOCARDIUM

The influence of sex on intrinsic contractile performance, diabetes-in duced myocardial mechanical dysfunction and the inotropic response to clinically relevant concentrations of ethanol (ETOH) was studied using weight-matched streptozotocin-induced diabetic rats. After 8 weeks, i solated left-ventricular papillary muscles stimulated at 0.5 Hz, were studied under isometric conditions at L(max). Peak developed tension, time-to-peak tension (TPT), time-to-90 % relaxation (RT(90)), and the maximum velocities of tension development and rate of tension decay we re assessed at baseline and in response to changes in stimulation freq uency and varying extracellular calcium concentrations. In male but no t in female rats, body weight and heart size were significantly correl ated with glycemic status. In both sexes, diabetes was associated with prolongation of baseline TPT and RT(90) values. However, diabetes-ind uced prolongations of contraction and relaxation duration were greater in papillary muscles obtained from male than in those from female ani mals. The negative staircase effect of increasing the frequency of sti mulation was not influenced by sex or the diabetic state. Similarly, n either the positive inotropic effect of increasing extracellular calci um nor the negative inotropic effect of ethanol was modified by sex or experimental diabetes. Our results suggest that: 1) myocardium from f emale rats is resistant to diabetes-induced myocardial dysfunction and 2) neither baseline developed tension, calcium-mediated nor ethanol-i nduced inotropic responsiveness are influenced by sex or experimental diabetes.