The excretion of renal enzymes during rest and exercise: a double-blind comparison between placebo and penbutolol

A double-blind cross-over study was carried out in five healthy male volunteers to investigate the renal tolerance of 40 mg penbutolol, a receptor-specific beta-blocking agent, during exercise and to compare its effects with a placebo. The effects of exercise were compared with a resting state after a medication on the placebo. Urine was collected in fractions for seven hours on each trial day. The urine volume and the excretion of alanine aminopeptidase (AAP), N-acetyl-beta-D-glucosaminidase (NAG) and gamma glutamyltransferase (GGT) per fraction were determined. The findings for the kidney enzymes AAP, NAG and GGT show that the renal tolerance of penbutolol was good. Physical exercise per se did not cause any increase in the excretion of the above-mentioned enzymes. Slight diurnal variation was seen in the excretion of the renal enzymes after both the placebo and penbutolol.