Captopril augments the renal response to an amino acid infusion in diabetic adults.

Abstract

This study examined whether patients with insulin-dependent diabetes mellitus and normal renal function have an altered response to an amino acid infusion when they are pretreated with a converting-enzyme inhibitor. Three groups of adults received amino acid infusions for 20 min on two occasions separated by a 240-min interval. Groups 1 (6 normals) and 2 (6 diabetics) ingested captopril (12.5 mg) 120 min before starting the second infusion. Group 3 (4 diabetics) did not receive captopril. Diabetics had normal base-line renal plasma flow, as indicated by para-aminohippuric acid clearance (CPAH), and glomerular filtration rate (GFR). In group 1, the maximum increase in CPAH was significant and similar with both infusions, 23 +/- 5 vs. 15 +/- 3% (SE); maximal changes in GFR were also significant and similar, 20 +/- 5 vs. 20 +/- 6%. In Group 2, the maximal increase in CPAH and GFR with the first infusion was 28 +/- 7 and 23 +/- 6%, respectively. After captopril, the increases in CPAH and GFR were significantly greater than with the first infusion (64 +/- 8%, P less than 0.002, and 67 +/- 9%, P less than 0.002, respectively). In Group 3 diabetics, there was no difference in either CPAH or GFR with the first vs. the second infusion. Thus captopril enhances the renal hemodynamic response to an amino acid load in diabetic patients but not in normal adults.