The Effects of Hypertension and Diabetes Mellitus on the Vascular Reactivity of Resistance Arteries

Abstract

We have studied the effects of both hypertension and streptozotocin-induced diabetes mellitus on alpha 1-adrenoceptor mediated vasoconstriction, endothelium-dependent and endothelium-independent vasodilation. The experiments were performed in perfused mesenteric vascular bed preparations taken from age-matched SHR, WKY, diabetic SHR and diabetic WKY. For the alpha 1-adrenoceptor agonist methoxamine, the mesenteric preparations from SHR and diabetic SHR yielded significantly (p < 0.05) stronger maximal responses than preparations taken from WKY and diabetic WKY, respectively. The diabetic state significantly (p < 0.05) decreased the responsiveness to methoxamine in arteries from SHR and WKY. Hypertension does not significantly change the concentration response-curves for (acetyl-beta) methacholine, histamine, adenosine diphosphate and sodium-nitroprusside. However, the sensitivity to endothelium-dependent vasodilation decreased in preparations from diabetic animals (< 0.05). It is concluded that mesenteric resistance arteries from SHR and diabetic SHR are more reactive to alpha 1-adrenoceptor stimulation, whereas diabetes reduces the responsiveness to methoxamine in WKY and SHR. Hypertension does not affect the endothelium-dependent relaxation in mesenteric arteries. However, diabetes decreases the sensitivity to endothelium-dependent relaxation without altering the sensitivity to sodium-nitroprusside. These findings are indicative of a diabetes-induced endothelial dysfunction in mesenteric resistance arteries. In preparations from diabetic hypertensive rats the reduced response to methoxamine and the endothelial dysfunction seem to run parallel.