The effects of intrarenal administration of isoproterenol on excretion of urinary enzymes were examined in dogs. Urinary N-acetyl-β-D-glucosaminidase (NAG) and glutamyl transpeptidase (γ-GTP) originated from lysosomes and the brush border membrane of the kidney, respectively. NAG excretion was elevated for 10 min by isoproterenol (0.2 µg/kg/min) without a drastic change in glomerular filtration rate and renal blood flow. This elevation was inhibited by pretreatment with d, l-propranolol (0.6 mg/kg bolus injection 0.3 mg/kg/30 min) but less so by d-propranolol. Urinary γ-GTP excretion was little affected by isoproterenol. In light of these findings, the possibility that β-receptors may be involved in the excretion of NAG has to be consid