Adaptation of the Weanling Rat to Diets Containing Excess Methionine

Abstract
High levels of L-methionine in the diet of weanling rats induced a severe growth depression for up to 5 days whereupon weight gain at a near normal rate occurred despite the animals' consumption of the same excess amino acid diet. Alterations in hepatic levels of cystathionine synthase, cystathionase, cysteinesulfinate carboxylase and serine dehydrase occurred concurrent with changes in the growth rate. Alterations in tissue levels of methionine and its metabolites directly paralleled enzymatic changes. From these studies we conclude that the rat adapts to excess dietary methionine by altering its metabolic response to the amino acid.