Vascular Reactivity in Experimental Diabetes Mellitus

Abstract

Vascular reactivity was examined in vessels of the perfused hindquarters of alloxan diabetic and control rats. A significant increase was noted in responsiveness of the diabetic animals to intra-arterial injection of epinephrine, norepinephrine, and synthetic angiotensin. No difference was observed in the vasoconstrictor effects of lumbar sympathetic nerve stimulation or intra-arterial administration of tyramine. Results obtained in diabetic animals were compared with those in animals treated with reserpine. It was found that the reserpinized animals exhibited increased vascular responsiveness only to the catecholamines, and not to angiotensin, vasopressin, tyramine, or barium chloride. Whereas the vascular smooth muscle of diabetic rats was sensitized to epinephrine and norepinephrine, isolated atria from these animals responded normally to the catecholamines. The 24-hour urinary excretion of the catecholamines was significantly elevated in diabetic animals. The data suggest that enhanced vascular reactivity seen in diabetic rats does not result from neuropathy of the sympathetic nervous system. The possible contributions of factors including alloxan per se and body weight to development of increased vascular reactivity in diabetes were considered, but the mechanism for the increase in vascular responsiveness remains unidentified.