CAPTOPRIL MAGNIFIES THE INCREASE IN ANGIOTENSIN I-CONVERTING ENZYME ACTIVITY IN RATS WITH AMINONUCLEOSIDE NEPHROSIS

1. Serum, tissue and urine angiotensin I-converting enzyme (ACE) activity was estimated in the following groups of rats: saline-injected rats (controls); captopril-treated (CAP) control animals (CONTROL-CAP); puromycin aminonucleoside (PAN)-induced nephrotic syndrome (NS); and CAP-treated animals with NS (NS-CAP). 2. Serum ACE activity increased in the CONTROL-CAP, NS, and NS-CAP groups. The increase in the NS-CAP group was significantly higher compared with the NS or CONTROL-CAP groups. 3. In the CONTROL-CAP group, tissue ACE decreased in brain, heart and adrenal glands, and remained unchanged in the lung, testis, kidney, small intestine and liver. In the NS group, tissue ACE activity increased in the lung and testis, decreased in the brain and heart, and remained unchanged in the small intestine, adrenal glands, kidney and liver. Tissue ACE activity increased significantly in the NS-CAP group compared with the other groups. This increase in tissue ACE may contribute to an increase in the serum ACE activity in the NS-CAP group compared with the NS group. 4. Urine ACE activity increased in the NS and NS-CAP groups, although the rise in the NS-CAP group was significantly higher. The urine ACE correlated significantly with the circulating levels of this enzyme in the NS and NS-CAP groups. The loss of ACE in the urine in the presence of an increased serum ACE activity indicates that the biosynthesis of tissue ACE and its release into the bloodstream must be elevated.