RENAL EXCRETION OF ZINC IN NORMAL INDIVIDUALS DURING ZINC TOLERANCE-TEST AND GLUCOSE-TOLERANCE TEST

The urinary excretion, renal clearance, and tubular reabsorption of zi nc were investigated in 30 adult healthy subjects under basal conditio ns and during the zinc and glucose tolerance tests. After a 12h overni ght fast, each subject was submitted to renal clearance of zinc. The p rocedures were performed between 8.00 and 12.00 a.m., after emptying t he bladder and ingestion of 4 ml deionized water/kg body weight at 8.0 0 a.m. The first urine sample was collected at 10.00 a.m., and the sec ond at 12.00 a.m. A dose of 110 mg ZnSO4.7H(2)O was administered orall y to each subject, diluted in 20 mi deionized water, at time 0 min. Bl ood samples were collected from an antecubital vein at times -30, 0, a nd 30 min and at 30 min intervals up to 240 min. Glucose was administe red intravenously (0.5 ml 50%/kg body weight) during the first 3 min o f the test, and blood samples were collected from an unconstricted, co ntralateral, antecubital vein at times -30, 0, 3, 5, 10, 20, 30, 45, 6 0, and 90 min. The results showed that urinary zinc excretion, and ren al zinc clearance were significantly higher during the zinc and glucos e tolerance tests than in the control condition. On the other hand, re nal zinc clearance was more elevated during the glucose tolerance test than during the zinc tolerance test. Variations in zinc tubular reabs orption and glomerular filtration rate were not detected. The results suggest that urinary excretion and renal clearance of zinc in healthy subjects increase during acute zinc ingestion and glucose infusion. Al though zinc ingestion raised urinary zinc excretion, glucose infusion was more effective in increasing renal zinc clearance. These normal pa rameters are important in the investigation of diabetic patients with serum and urine zinc changes.