Increased arginase activity during lymphocyte mitogenesis

A sensitive assay for arginase activity was developed using guanidino-¹⁴C]arginine as substrate and measuring the production of ¹⁴CO₂ from ¹⁴C]urea in the presence of urease. Arginase activity was measured in bovine lymphocytes after activation by Concanavalin A. The specific enzymatic activity of arginase doubled in 6 hours and increased nearly 4-fold by 24 hours after stimulation. It is suggested that the role of arginase in these cells is to provide ornithine as substrate for the synthesis of putrescine, precursor of the polyamines spermidine and spermine.