Circadian variation of urinary enzymes in the dog

Circadian variations of N-acetyl-beta-D-glucosamidase (NAG, EC 3.2.1.30) and gamma-glutamyl transpeptidase (gamma-GTP, EC 2.3.2.2) were examined in dogs. Urine and blood were collected at 4-hr intervals from adult mongrel dogs (11 males, 11 females) weighing between 7 and 13 kg. The collected urine and blood were used to measure creatinine, NAG and gamma-GTP. The amount of urine was significantly higher (p < 0.05) during the period from 12:00 to 16:00. Creatinine clearance did not show any characteristic variations and creatinine excretion was significantly higher (p < 0.05) during the period from 8:00 to 16:00. No characteristic variations were observed in the amounts excreted, activity, or NAG and gamma-GTP creatinine index. There were high correlations between creatinine excretion and creatinine clearance (r = 0.693), gamma-GTP excretion and gamma-GTP creatinine index (r = 0.724), NAG excretion and NAG creatinine index (r = 0.878), and between the NAG and gamma-GTP creatinine index of each 4-hr specimen and the NAG and gamma-GTP excretion of the 24-hr specimens. These results suggest the diagnostic usefulness measuring enzyme activity in non-periodically collected urine.