Effects of folic acid and methotrexate on arginase activity in regenerating rat liver tissue.

Arginase (L-arginine-ureidohydrolase, EC 3.5.3.1) catalyses the hydrolysis of arginine to ornithine and urea. Its primary metabolic role is to remove the excess of ammonia through synthesis of urea. Ornithine, as a product of arginase reaction can be used for synthesis of polyamines. Rapid tissue growth after partial hepatectomy is accompanied by an increase in biosynthesis of polyamines. The aim of this study was to examine the importance of arginase in regenerating liver after partial hepatectomy and to investigate the influence of folic acid and methotrexate on arginase activity on this model of compensatory growth. It was established that arginase activity was significantly reduced in regenerating rat liver tissue at different time intervals after partial hepatectomy. Administration of folic acid to hepatectomized rats led to inhibition of arginase activity. Administration of methotrexate after hepatectomy increased the arginase activity.