Serum angiotensin converting enzyme activity in normal adults and patients with different types of hypertension.

The serum converting enzyme activity (SCEA) was measured in 86 healthy individuals (1.44 +/- 0.82 u, mean +/- SD), 39 patients with essential hypertension (1.53 +/- 0.71 u), 7 patients with hypertension due to renal artery stenosis (1.76 +/- 0.77 u), 14 patients with chronic renal failure (2.10 +/- 0.57 u), 7 patients with renal failure and hypertension (2.62 +/- 0.35 u), 22 normotensive pregnant women (1.02 +/- 0.26 u) and 6 hypertensive pregnant women (1.1 +/- 0.3). No difference was detected between men and women or between normotensives and hypertensives. However, a significant rise in SCEA was found in patients with chromic renal failure (P less than 0.005), in whom an enlarged pulmonary vascular bed and accelerated cellular breakdown are thought to be the causes of the elevated SCEA. During pregnancy, subnormal SCEA was found (P less than 0.005), and this is thought to be due to the enzyme consumption in the kinin system, which is activated during pregnancy. We assume that converting enzyme is not a limiting factor in angiotensin conversion, and most probably it does not contribute significantly to the pathogenesis of hypertension.