ASSAY OF ORNITHINE CARBAMOYL TRANSFERASE-ACTIVITY - MODIFICATION FOR APPLICATION TO BOVINE SERUM

An assay procedure for ornithine carbamoyl transferase (OCT), which is known to be a liver-specific enzyme, was modified to be adaptable to bovine serum. The concentration of carbamoyl phosphate and the pH of t he reaction reagent solution shifted to 60 mM and 7.2, respectively. T hese modifications contributed to the augmentation of assay sensitivit y. The day-to-day reproducibility was 7.9% (coefficient variation) for serum with high OCT activity and 14.8% for normal bovine serum. The a ctivity was stable for 3-4 months by the storage at -20-degrees-C and at least 6 months at -80-degrees-C. The OCT activity and other biochem ical components including aspartate aminotransferase and gamma glutamy l transpeptidase were measured in sera from 164 dairy or raising cows reared at 7 farms. The normal level of OCT activity in sera from these cows ranged from 9.2 to 25.1 U/l (mean +/- 2SD). By comparison betwee n the farms, the highest mean value of OCT activity was found in a far m where cows were suspected to have some kind of latent liver disease from the data of other biochemical parameters. We conclude that the OC T activity is a very useful diagnostic indicator of liver disease in c attle.