Alterations in cardiac performance in experimentally-induced diabetes.

Responses in cardiac tissue isolated from streptozotocin (STZ)-treated and age-matched control rats to isoproterenol (ISO) and calcium were studied. 4 weeks after STZ, atrial function was found to be depressed, whereas right ventricular function was enhanced. Neither tissue exhibited an alteration in sensitivity to ISO. In contrast, while sensitivity to calcium was found to be unaltered in atrial tissue, supersensitivity to calcium was observed in ventricles after STZ treatment. beta-Adrenoceptor number determination revealed a 36% decrease in Bmax with no change in affinity after STZ treatment. These results suggest that 4 weeks after STZ treatment pacemaker function is depressed, while enhancement in ventricular function is associated with an alteration in calcium utilization.