AN ARGINASE INHIBITOR(S) AND ITS POSSIBLE ROLE IN THE DEVELOPMENTAL DECREASE OF ARGINASE ACTIVITY IN CHICK EMBRYOS

Abstract

1. Arginase activity was measured in tissues of developing eggs from the first to the seventh day of incubation. Activity per unit moist weight or dry weight decreased in embryo, pellucida, vasculosa and vitellina. 2. Evidence was obtained that all chick tissues studied contain a high molecular weight arginase inhibitor(s) which appears to be ribonucleic acid in nature. 3. Inhibitor(s) seems to play a major role in establishing the level of arginase activity expressed by crude homogenates. 4. The decreased arginase activity of hearts from developing embryos has been correlated with an increase in inhibitor activity. 5. These results suggest that the developmental decrease in arginase activity could be the result of an increase in inhibitor concentration as well as of a decrease in enzyme concentration.