The effect of threonine deficiency on the synthesis of some phosphorus fractions in the rat.

Rats on diets containing suboptimal amounts of threonine or lysine have been observed to develop fatty livers, which could be controlled by adequate dietary levels of these amino acids (2). Choline was also lipotropic, but only at high levels, at which its activity was still limited in extent. The liver lipide pattern in these amino acid deficiencies was found to be suggestive of that observed in typical choline deficiency in rats on high fat, low protein rations. The lipotropic action of choline in the latter circumstance has been explained by an increased phospholipide turnover in the liver (3). It was, therefore, of interest to study the rate of incorporation of radiophosphorus into the phospholipide and the protein-bound phosphorus fractions of liver, small intestine, and kidney of threonineor lysine-deficient rats in order to elucidate the relationship between these amino acids and choline. The results of the threonine deficiency study are presented here.