Effect of ethionine and fasting on the free amino acids of rat liver.

Little is known concerning the effect of biological antagonists on the concent,ration of tissue metabolites in vivo. Yet such knowledge would seem to be a prerequisite to understanding the physiological action of an antimetabolite. It has been observed that the concentration of some free amino acids in rat liver increased after prolonged treatment of the animals with m-ethionine (I). In the work reported here, the concentration of a number of amino acids in rat liver was determined at various times after a single injection of ethionine. In order to relate the action of the antagonist to the exogenous and endogenous supply of amino acids, experiments were conducted with both fed and fasted animals. Such studies may help to explain the retarding effects of ethionine on the growth of normal and tumor tissue of rats (1).