Biphasic alteration of renin-angiotensin-aldosterone system in streptozotocin-diabetic rats

The alteration of renin-angiotensin-aldosterone system caused by diabetes mellitus was studied in streptozotocin-diabetic rats. The plasma renin activity (PRA), and plasma levels of angiotensin II (A II) and aldosterone (PAC) were measured in diabetic and age-matched control rats in 1, 2, 4 and 8 weeks after the intravenous injection of streptozotocin (50 mg/kg body weight). Diabetic rats showed the marked hyperglycemia persistently throughout the experimental period. On 1st week PRA, A II and PAC were significantly increased, and A II and PAC were also significantly elevated on 2nd week in diabetic rats compared with control rats. However, on 4th and 8th weeks PRA, A II and PAC in diabetic rats were significantly lower than those of control rats. Hematocrit values in diabetic rats were elevated on 1st week, normalized on 2nd and 4th weeks and then decreased on 8th week. These results may suggest that the hyperglycemia causes a biphasic alteration of renin-angiotensin-aldosterone system, i.e., early stimulated state due to volume depletion and later suppressed state due to volume expansion.