WHICH URINARY PROTEINS ARE DECREASED AFTER ANGIOTENSIN CONVERTING-ENZYME INHIBITION

It is believed that angiotensin converting-enzyme (ACE) inhibitors low er proteinuria by acting on glomerular hemodynamics. This hypothesis p redicts that the urinary excretion of a tubular protein should be unaf fected by ACE inhibition, in the present study we have compared the ex cretion of albumin and Tamm-Horsfall Glycoprotein (THGP), a protein se creted only by renal tubules, before and after ACE inhibition. Urinary protein excretion was measured with the Phast System, a method based on SDS polyacrylamide gel electrophoresis followed by silver staining, in 15 essential hypertensives, after at least 4 weeks of wash-out fro m any drug and after 2 months of ACE inhibition with oral Quinapril. A fter 2 months of ACE inhibition, blood pressure (BP), body weight, uri nary output, heart rate, plasma glucose, plasma and urinary creatinine , urate and electrolytes, and creatinine clearance, were not different from baseline values. Plasma ACE activity decreased from 76 +/- 7 to 10 +/- 4 U/mL (mean +/- SEM, 2 tails paired t test, p = 0. 0001). Both albumin and THP urinary excretions decreased from 51 +/- 6 to 43 +/- 4 mg/24 h (p = 0.05) and from 19 +/- 3 to 12 +/- 1 mg/24 h (p = 0.02), respectively. This unexpected result suggests that ACE inhibitors may act also at the level of renal tubular cells.