ESTIMATION OF QUANTITATIVE ENZYMURIA IN DOGS WITH GENTAMICIN-INDUCED NEPHROTOXICOSIS USING URINE ENZYME CREATININE RATIOS FROM SPOT URINE SAMPLES

The correlation between 24-hour urinary excretion of N-acetyl-beta-D-g lucosaminidase (NAG) and gamma-glutamyl transferase (GGT) with urine N AG and GGT/creatinine ratios was assessed in dogs with gentamicin-indu ced nephrotoxicosis. Eighteen 6-month-old male Beagles with normal ren al function were randomly divided into 3 groups of 6. Each group was f ed a different concentration of protein (high protein, 27.3%; medium p rotein, 13.7%; and low protein, 9.4%) for 21 days. After dietary condi tioning, gentamicin was administered at a dose of 10 mg/kg IM tid for 8 days and each group was continued on its respective diet. Endogenous creatinine clearance and 24-hour urinary excretion of NAG and GGT wer e determined after dietary conditioning (day 0) and on days 2, 4, 6, a nd 8 of gentamicin administration. In addition, urine NAG and GGT/crea tinine ratios (IU/L divided by mg/dL) were determined from catheterize d spot urine samples obtained between 7 and 10 AM on the same days. Th e correlation between 24-hour urinary enzyme excretion and urine enzym e/creatinine ratio in the spot urine samples was evaluated by simple l inear regression analysis. Spot sample urine enzyme/creatinine ratios were significantly correlated with 24-hour urinary enzyme excretion th rough day 4 for dogs on low dietary protein, through day 6 for those o n medium protein, and through day 8 for those on high dietary protein. Mean +/- SD baseline values for urine NAG/creatinine ratio and 24-hou r urinary NAG excretion were 0.06 +/- 0.04 and 0.19 +/- 0.14 IU/kg/24 hr, respectively. Baseline values for urine GGT/creatinine ratio and 2 4-hour urinary GGT excretion were 0.39 +/- 0.18 and 1.42 +/- 0.82 IU/k g/24 hr, respectively.