Pathophysiology of increased urinary N-acetyl-beta-D-glucosaminidase activity in human hypertension: effect of cilazapril therapy.

To investigate the pathophysiology of elevated urinary N-acetyl-beta-D-glucosaminidase (NAG) activity in human hypertension, total and fractional urinary NAG activities were correlated with Li clearance, a measure of proximal renal tubular Na reabsorption, in 15 white hypertensive subjects, aged 56 years, and in 13 normotensive control subjects. In 11 hypertensive subjects, the measurements were repeated after 2 months of antihypertensive therapy with the converting enzyme inhibitor cilazapril (2.5 or 5.0 mg daily). Urinary NAG activity was increased in hypertensives and correlated directly with Li clearance in both hypertensive and normotensive subjects. Li clearance and urinary NAG activity were reduced by antihypertensive therapy. The findings indicate an inverse correlation between urinary NAG activity and proximal renal tubular Na reabsorption, suggesting that NAG is reabsorbed in the proximal renal tubules with Na and other proteins. High Li clearance and urinary NAG activity in hypertension are in part functional and, therefore, reversible disturbances of renal function.