Effect of captopril on renal function in patients with essential hypertension

The glomerular filtration rate (creatinine clearance), glomerular permeability (qualitative and quantitative proteinuria), tubular reabsorption (k-lambda chains of immunoglobulins and lysozyme) and indexes of tubular cell lysis (alpha-glucosidase and gamma-glutamyltranspeptidase) were measured in the urine of 10 patients with moderate, uncomplicated essential hypertension during placebo therapy and after captopril given at increasing doses of 25, 50, 100 and 200 mg twice daily, the first three doses being given for 3 days and the last one for 4 weeks in all patients and for an additional 6 months in 5 patients. During placebo therapy, proteinuria was absent in eight patients and detectable (glomerular and selective) in two; selective proteinuria appeared in two and a decrease in selectivity was observed in two patients with previous proteinuria after 4 weeks of captopril therapy. No proteinuria was detectable in the five patients followed up to 6 months, not even in the one in whom a decrease in glomerular selectivity had occurred after 4 weeks. The glomerular filtration rate was unchanged as were lysozyme and gamma-glutamyltranspeptidase values, while light chains were always undetectable. Alpha-glucosidase showed some increase; however, increments were transient and always much lower than those observed with known tubular toxic drugs. These data show that under our experimental conditions captopril caused no evident changes in glomerular and tubular function.