To reveal the mechanism of hypertension in diabetes mellitus, changes in blood pressure were measured in streptozotocin (STZ)-induced diabetes mellitus in male Wistar rats. Development of diabetes mellitus and elevation of blood pressure were observed in rats which received 60 mg/kg STZ, but not in rats which received 20 mg/kg STZ. In the rats which developed diabetes mellitus after STZ, the plasma renin activity, renal renin content, plasma aldosterone, and urinary kallikrein activity were all significantly reduced. The urinary excretion of prostaglandin E2 (PGE2) was significantly increased at 1 week after STZ in diabetic rats, but it gradually returned to control values and showed a tendency to decrease at 4 weeks after the treatment compared to the rats of the control groups. The pressor responsiveness to norepinephrine in the conscious unrestrained state in the STZ-induced diabetic rats was not remarkably changed compared to that of control rats. These results indicate that blood pressure gradually increases with the progress of diabetes. It is suggested that the changes in urinary excretion of PGE2 and urinary kallikrein activity may be related to the regulation of blood pressure in STZ-induced diabetic rats. On the other hand, it is considered unlikely that the reninangiotensin system and vascular responsiveness play an important role in the occurrence of hypertension in diabetes mellitus.
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