Influence of Short-Term Experimental Diabetes on Blood Pressure and Heart Rate in Response to Norepinephrine and Angiotensin II in the Conscious Rat

Hypertension, atherosclerosis, arteriosclerosis, and cardiomyopathy account for 80% of all diabetic deaths. A paucity of data exists concerning reactivity of the diabetic vasculature to vasopressor substances. The purpose of this investigation was to determine the influence of short-term (4-5 weeks) diabetes on the responsiveness of the cardiovascular system to vasopressor substances in the intact conscious rat. Diabetes was chemically induced with streptozotocin (65 mg/kg i.v.) in 42-43-days-old, nonfasted, male Sprague-Dawley--derived rats. Direct blood pressure and heart rate were recorded, and responses to the vasopressor agonists norepinephrine and angiotensin II were obtained. Short-term diabetic rats were hypotensive and had lower heart rates when compared with control rats. Blood pressure responses to norepinephrine and angiotensin II were depressed in the short-term diabetic rat; however, the baroreceptor reflexes in these rats were more sensitive to increases in blood pressure. Therefore, it appears that there is some type of nonspecific alteration in the responsiveness of the cardiovascular system to the vasopressor agonists in the short-term diabetic rat.