Streptozotocin-Induced Diabetes Mellitus Lowers Blood Pressure in Spontaneously Hypertensive Rat

There are conflicting reports showing that alloxan or streptozotocin-induced diabetes in rat increases, decreases or does not alter blood prassure. Since hypertension influences organ-specific diabetic complications, this study was designed to examine the effects of streptozotocin-induced diabetes on blood pressure (BP), hemodynamics and heart weight in spontaneously hypertensive (SHR) and normotensive Wistar (NWR) rats. In order to control the influence of weight loss on BP affected by diabetes, we have examined the effect of weight loss without diabetes on BP, hemodynamics and heart weight in SHR. Weight loss parallel to that in diabetic SHR was induced in a group of SHR by food restriction (fasting). Significant (P< .05) decreases in systolic and direct BP were observed in diabetic SHR. This hypotensive effect was accompanied by a significant (P < .05) decrease in total peripheral resistance, but no change in cardiac output. These blood pressure and hemodynamic findings in diabetic SHR were complimented by a significant (P < .05) reduction in left ventricular weight to body weight ratio. On the contrary, fasting SHR with weight loss equivalent to that in diabetic SHR showed no change in BP or total peripheral resistance. Further, fasting SHR revealed a significant (P < .05) increase in heart weight to body weight ratio. The weight loss of equal magnitude induced by streptozotocin-induced diabetes in NWR did not have any effect on BP or hemodynamics. In addition, like fasting SHR, diabetic NWR showed a significant (P < .05) increase in left ventricular weight to body weight ratio. This study concludes that streptozotocin-induced diabetes significantly reduces BP independent of weight loss in SHR, and that the hypotensive effect is the result of peripheral vasodilatation.