Distribution of arginase in tissues of cat (Felis catus)

Arginase (EC 3.5.3.1), the final enzyme in the urea cycle, catalyses the hydrolysis of l-arginine to l-ornithine and urea. High activity of this enzyme in the liver indicates its primary role in ammonia detoxification. However, its wide tissue distribution suggests that this enzyme might perform other functions besides hepatic ureagenesis. Although the distribution and properties of arginase from many tissues of human, laboratory animals and some domestic animals have been studied, little is known about the pattern of distribution and physiological roles of this enzyme in the cat. The purpose of this study was to examine and compare the distribution of arginase in different tissues of the cat. A selection of tissue samples was assayed for arginase by the diacetyl monoxime method of determination of enzymatically formed urea. The protein content of tissues and enzymatic activities were calculated as units per gram tissue and units per milligram protein of the tissue. Results showed that the liver was the richest source of arginase followed by the oesophageal and tongue mucosal layers. Significant activity of this enzyme was found in the mucosa of the small intestine, kidney cortex, lung, testis and ovary. The results of this study will be discussed in terms of the involvement of arginase in several biochemical and physiological functions in this species.