Angiotensin-converting enzyme activity in renal disorders: influence of disease pattern, hemodialysis and transplantation.

Serum angiotensin-converting enzyme activity (s-ACE) was measured spectrophotometrically in a variety of renal disorders. In 111 renal patients not on dialysis, s-ACE was slightly lower (22.9 +/- 5.9 U/ml; mean +/- SD) than in 116 controls 24.4 +/- 6.2 U/ml). In 52 patients on chronic hemodialysis s-ACE was 24.1 +/- 4.7 U/ml; serial analyses done before initiation of chronic dialysis showed a significant increase in s-ACE levels towards normal values. In 38 renal allograft recipients s-ACE was relatively low (22.0 +/- 5.0 U/ml); a significant decrease in s-ACE was observed in patients followed from the time of transplantation (24.6 +/- 6.4 U/ml) to two weeks after transplantation (20.2 +/- 4.5 U/ml). S-ACE was also depressed (17.4 +/- 2.6 U/ml) in 12 patients with acute renal failure, and it increased in parallel with normalization of renal function. S-ACE was normal (24.4 +/- 5.7 U/ml) in 14 patients with essential hypertension. Elevated s-ACE (above mean of controls + 2 SD) was observed in only one patient of the total series. We could not confirm previous reports on elevated s-ACE in dialysis patients, but several factors invalidate a direct comparison between series. Thus, the deviations in s-ACE in renal disorders seem to be discrete: depressed levels in acute renal failure and a relative depression in undialyzed patients with chronic renal disorders. The low activity after transplantation may be secondary to the immunosuppressive treatment.