Recent studies have demonstrated that short-term angiotensin converting enzyme (ACE) inhibition with captopril can reduce urinary albumin excretion rate (UAER) after exercise in normotensive diabetic patients with early-stage nephropathy. The aim of this study was to investigate whether this effect of ACE inhibition was due to a systemic hypotensive action or a specific action at the intrarenal level. Thus, we compared the acute effects of captopril and the Ca2+-channel blocker nifedipine on exercise-induced UAER in normotensive (blood pressure <165/95 mmHg) diabetic patients who were normoalbuminuric or microalbuminuric at rest (stage 2 or 3 of diabetic nephropathy). Twenty-five stage 2 diabetic nephropathy patients, 39 stage 3 diabetic nephropathy patients, and 12 nondiabetic subjects performed five submaximal cycloergometric exercises (90% of theoretical heart rate) on nonconsecutive days. The first two exercises were performed in basal conditions; the next three exercises were performed 24 h after administration of captopril (25 mg twice daily) or nifedipine AR (20 mg twice daily) or placebo (1 tablet twice daily) according to a randomized double-blind crossover trial. After placebo, blood pressure and UAER did not change at rest or 1 h after exercise. After captopril, blood pressure at rest and during exercise was similar to that observed after placebo. UAER at rest was not modified, whereas 1 h after exercise, it was significantly decreased both in stage 2 and stage 3 diabetic nephropathy patients (P < 0.001). After nifedipine, blood pressure decreased significantly at rest and during exercise in respect to placebo and captopril. UAER at rest did not change significantly. UAER 1 h after exercise was significantly decreased both in stage 2 and stage 3 diabetic nephropathy patients (P < 0.01 vs. placebo), but it was significantly higher than that observed after captopril (P < 0.01). Captopril is more effective than nifedipine in reducing exercise-induced UAER in normotensive diabetic patients even though it does not influence blood pressure response to exercise. The effects of captopril on UAER induced by exercise may be due to a specific action at the intrarenal level.

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