ANGIOTENSIN-CONVERTING ENZYME-ACTIVITY IN THE SERUM, LUNG AND KIDNEY OF DIABETIC RATS

Diabetes Mellitus in its early stages, is associated with kidney enlar gement and increased glomerular filtration rate in humans and in rats. The present study was designed to clarify the direct effect of diabet es on serum and tissue angiotensin converting enzyme (ACE) activity in streptozotocin-induced diabetic rats. Serum ACE activity, as determin ed using a radiometric assay, was significantly increased in the diabe tic rats (n = 15) 14 days after induction of diabetes (670 +/- 31 vs. 506 +/- 14 nmol ml-1 min-1). Lung ACE activity, but not renal, was sig nificantly elevated at 7 and 14 days by 29 and 46%, respectively. Plas ma renin activity in the diabetic rats was decreased at 7 and 14 days by 41 and 78%, respectively. Incubations of lung slices in the presenc e of glucose at different concentrations did not affect in-vitro relea se of the enzyme. Administration of insulin (8 units kg-1) to diabetic rats (n = 6) on the 4th day for 11 days reduced ACE activity to value s below control. Thus, serum and lung ACE activity is increased in the diabetic rat and reduced upon insulin treatment.