INVITRO DETERMINATION OF THE EXTENT OF HYDROLYSIS OF HOMOARGININE BY ARGINASE IN THE SMALL-INTESTINE OF THE GROWING RAT

The extent of hydrolysis of free homoarginine, catalyzed by arginase, in the small intestine of the growing rat was determined in an in vitro experiment. Synthetic L-homoarginine was added to digesta collected from the small intestine of growing rats or to a supernatant prepared from digesta. The material was incubated under CO2 at pH 7.3 and a temperature of 38-degrees-C for 4 h. Following incubation, there was no change in the concentrations of homoarginine or lysine, in either the supernatant or the digesta samples. The lysine concentration did not alter, regardless of whether or not homoarginine was added to the material before incubation. Further evidence for a lack of arginase activity under these conditions was the constancy of the arginine concentration. The results supports the use of guanidinated proteins for determining endogenous ileal lysine flows in animals.