Effect of diabetes on metabolic coronary dilatation in the rat

There is increasing evidence that patients with diabetes mellitus are prone to ischaemic heart disease. This study examined cardiac hyperactivity and its consequent metabolically induced coronary dilatation in isolated, perfused, electrically paced rat hearts from control and spontaneously diabetic Bio-Breeding (BB) rats. Cardiostimulation produced by noradrenaline, calcium, or by tachycardia elicited increases in coronary flow that were significantly lower in diabetic hearts. However, the inotropic responses to noradrenaline and calcium in diabetic preparations were comparable to control. When coronary vascular reactivity was tested with sodium nitroprusside and adenosine, a decreased dilator response was observed with adenosine in diabetic hearts while no difference was observed with sodium nitroprusside. It is suggested that failure in the adaptive coronary flow response to cardiac hyperactivity in diabetes may, in part, be responsible for the higher incidence of ischaemic heart disease in the diabetic population.