Effects of enalapril and nitrendipine on exercise albuminuria in normotensive type I diabetic patients with incipient nephropathy.

Based on animal experiments it has been proposed that antihypertensive agents may differentially influence albuminuria through their divergent effects on glomerular haemodynamics or glomerular sieving properties and may beneficially influence the progression of diabetic nephropathy even without an effect on blood pressure. However, to date this hypothesis has not been tested in normotensive patients with diabetic nephropathy. The main aim of this study was therefore to investigate the effects of the administration of two antihypertensive agents on albuminuria during rest and exercise. The study consisted of 3 x 3 randomised, cross-over periods with five days double blind administration of enalapril (E: 2.5 mg bid), nitrendipine (N: 5 mg bid) and placebo (P) on 18 Type 1 normotensive (blood pressure < 140/90 mmHg) diabetic patients with incipient diabetic nephropathy (albuminuria 30-300 mg/24 h, normal glomerular filtration rate, diabetes duration > 6 years and presence of diabetic reinopathy. The aim of this study was to investigate the effect of enalapril and nitrendipine on blood pressure values and albuminuria during exercise challenge (bicycle ergometry: 20 min at 75 W and 20 min at 100 W) in comparison to the placebo. Albumin excretion rates during pre-exercise rest (mean +/- SD; E: 6.2 +/- 6.0; N: 7.1 +/- 8.0; P: 7.7 +/- 7.0 mg/mmol creatinine) and during exercise (E: 8.7 +/- 9.4; N: 8.2 +/- 8.2; P: 11.1 +/- 11.4 mg/mmol creatinine) were comparable between the drugs and not significantly different after administration of placebo. Blood pressure values were significantly different between the medications (systolic blood pressure: p = 0.0269; diastolic blood pressure: p = 0.0021, ANOVA for repeated measurements). There were no significant correlations between blood pressure values and albuminuria at any time. In normotensive patients with incipient diabetic nephropathy low-dose administration of enalapril, nitrendipine and placebo does not result in clear cut differences in albuminuria.