LACK OF EFFECT OF CAPTOPRIL ON GLOMERULAR HYPERFILTRATION IN NORMOALBUMINURIC NORMOTENSIVE INSULIN-DEPENDENT DIABETIC-PATIENTS

The aim of the present study was to evaluate the effects of captopril on the glomerular filtration rate (GFR) and urinary albumin excretion rate (UAER) of normoalbuminuric normotensive insulin-dependent diabete s mellitus (IDDM) patients with and without glomerular hyperfiltration . Eleven normoalbuminuric (UAER < 30 mu g/min) patients (age: 34.3 +/- 4.6 years; diabetes duration: 9.5 +/- 6.4 years) participated in the study. Six patients were considered to be hyperfiltering (GFR greater than or equal to 134 ml/min/1.73 m(2)). GFR (Cr-51-EDTA single injecti on technique), extracellular volume (ECV; distribution volume of Cr-51 -EDTA), UAER (RIA) and metabolic and biochemical parameters were measu red at baseline, after 6 weeks on captopril (25 mg p.o. twice daily) a nd after 6 weeks off captopril. plasma renin activity (PRA; RIA), plas ma aldosterone (RIA) and blood volume (Cr-51 red cell labeled) were me asured at baseline and after 6 weeks on captopril. The baseline clinic al and laboratory characteristics of hyperfiltering and normofiltering IDDM patients were similar. GFR did not change during the study (144. 1 +/- 28.8; 139.7 +/- 21.8; 132.8 +/- 29.9 ml/min/1.73 m(2)) either in patients with hyperfiltration (164.6 +/- 20.7; 153.8 +/- 18.3; 148.6 +/- 31.0 ml/min/1.73 m(2); n = 6) or without hyperfiltration (119.6 +/ - 11.1; 123.2 +/- 11.9; 113.8 +/- 14.4 ml/min/1.73 m(2); n = 5). Also, ECV (22.2 +/- 3.6; 21.5 +/- 4.3; 21.5 +/- 3.5 L/1.73 m(2)), UAER (3.9 [0.4-22.1]; 4.0 [0.2-11.4]; 3.7 [2.0 - 26.2] mu g/min), systolic (112 +/- 13; 105 +/- 10; 111 +/- 11 mmHg) and diastolic (76 +/- 12; 72 +/- 9; 73 +/- 12 mmHg) blood pressure did not change. No difference in bl ood volume (60.8 +/- 10.4; 62.3 +/- 8.4 ml/kg) or plasma aldosterone ( 10.4 +/- 4.9; 7.7 +/- 3.8 ng/dl) was observed between baseline values and values after captopril use. PRA increased (2.4 [0.4-22.1]; 12.9 [2 .2-41.1]ng/ml/h) at the end of 6 weeks on captopril (P=0.002). Fasting plasma glucose, glycated hemoglobin, fructosamine, plasma cholesterol and potassium, 24 h urinary urea and sodium were similar during the s tudy. These results were unchanged when patients with and without hype rfiltration were analyzed as separate groups. From baseline to the end of 6 weeks on captopril there was no correlation between change in GF R and change in glycated hemoglobin (r = 0.02, P = 0.96), systolic (r = 0.23; P = 0.49) and diastolic (r = - 0.32, P = 0.32) blood pressure, urinary urea (r = 0.21; P = 0.53) and UAER (r = - 0.16; P = 1.00). In conclusion, captopril has no effect on the GFR and UAER of normoalbum inuric normotensive IDDM patients irrespective of the presence of glom erular hyperfiltration.