Kidney arginase activity in chicks fed diets containing deficient or excessive concentrations of lysine, arginine, histidine, or total nitrogen.

Three experiments were conducted with 1 to 2-week-old chicks fed purified crystalline amino acid diets. Kidney arginase activity increased substantially when total dietary nitrogen exceeded the dietary requirement for maximal chick weight gain. Single deficiencies of either histidine or lysine in nitrogen-adequate diets also resulted in marked increases in enzyme level. Arginine deficiency resulted in a slight increase in arginase activity, but the magnitude of the increase appeared to have little effect on efficiency of arginine utilization. Further, the response could be prevented by making lysine and arginine equally limiting. Increasing the lysine:arginine ratio to two in a nitrogen-deficient diet did not increase arginase activity. The same ratio in a arginine- and nitrogen-adequate diet resulted in a twofold increase in arginase activity accompanied by reductions in rate and efficiency of weight gain.