THE VARIATION IN EXCRETORY URINARY GLYCYL-PROLYL DIPEPTIDYL AMINOPEPTIDASE IN DOGS

We studied the excretory variation of urinary glycyl-prolyl dipeptidyl aminopeptidase (GP-DAP, EC 3.4.14.5) in dogs. Adult domestic mongrel dogs (seven males and nine females, 7.5 to 13 kg bodyweight) which wer e considered to be healthy by laboratory tests were used. Urine and bl ood samples were obtained every four hours. Urine volume was measured for each sample and urine GP-DAP activity, and creatinine levels were determined. Creatinine clearance, creatinine excretion, GP-DAP activit y and GP-DAP index (GP-DAP/Cr ratio) did not show any significant vari ation between the time periods. However, urine volume and urinary GP-D AP excretion significantly increased from 8:00 am to 12:00 pm. The GP- DAP index in spot urine samples showed low correlation with 24 hour GP -DAP excretion. In addition, a sex difference was observed in GP-DAP e xcretion. In conclusion, urinary GP-DAP excretion showed a circadian v ariation and sex difference. Therefore, GP-DAP in spot urine is not of use for the detection of renal disorders, and the 24-hour excretion v alue of GP-DAP should be determined.