Urinary excretion of converting enzyme in pyelonephritis.

Angiotensin converting-enzyme (ACE) is located in the brush border of kidney tubules. Owing to this localization and the high molecular weight of the enzyme, urinary ACE activity should represent a good index of tubular damage. Urinary ACE activity has been evaluated in 5 groups of subjects: 30 control, 21 pyelonephritic, 21 glomerulonephritic, 9 cystitic and 7 hypertensive. The mean values were 33.23 ± 37.2 SE μmoles His-Gly/g creatinine in control 277.94 ± 34.2 in pyelonephritic, 57.87 ± 17.8 in cystitic and 57.34 ± 10.9 in hypertensive subjects. An analysis of variance showed that urinary ACE activity was significantly higher than normal only in pyelonephritic patients (F = 26.5; p < 0.005). Moreover the percentage of abnormal urinary ACE activity (greater than the mean ± 2 SD of the control value) was 95.2 ± 4.4 in pyelonephritics, 28.5 ± 9.4 in glomerulonephritics, 33.3 ± 15.4 in hypertensives and 14.2 ± 13 in patients with lower urinary tract infection, being significant only for the pyelonephritic group (χ2 = 25.52; p < 0.0005). According to these data urinary ACE activity seems to be a good index of renal tubular damage.