Determination of serum arginase in an animal model of liver necrosis

ABSTRACT

Arginase catalyzes the conversion of arginine to urea and ornithine in the liver of ureotelic animals. Higher activity of this enzyme has been detected in the sera of patients with hepatic diseases. Many difficulties inherent in current methods for arginase have hampered widespread use of this enzyme as a liver function test. We have developed a simple colorimetric method for determination of arginase. This method is based on the determination of remaining arginine, after its conversion, by reaction with p-nitrophenyl glyoxal [PNPG] at pH 9.0 to produce a color which absorbs maximally at 480 nm. The decrease in the absorbance in the presence of arginase is correlated with the enzyme activity. In this simple method color development as well as termination of enzyme activity is achieved by addition of a single reagent, i.e. PNPG, to the incubation mixture, thereby obviating the use of many chemicals ordinarily used in other methods for arginase. This method was used to measure the level of arginase in the sera of animals in which liver necrosis had been experimentally induced by oral administration of carbon tetrachloride, The results were compared with other enzyme that are currently used for liver function test. No arginase could be detected in the sera of healthy animals. Serum arginase elevated after 6 hours following administration of carbon tetrachloride, reached highest level after 24 hours and returned to normal at 72 hours. A similar pattern was observed for alkaline phosphatase and rhodanese, while the level of AST remained elevated for 48 hours and declined gradually thereafter. The Implication of these studies in human medicine are discussed