Liver Polysome Patterns of Rats Fed Amino Acid Imbalanced Diets

Abstract

The response of rat liver polysomes to administration of isoleucine-and threonine-imbalanced diets has been investigated. The control diets were prepared with low levels of crystalline amino acids limiting in either isoleucine or threonine. To these control diets were added mixtures of amino acids lacking respectively isoleucine or threonine (imbalanced diets), or the same amino acid mixtures with threonine or isoleucine added to them (corrected diets). In the first series of experiments, all the rats were trained for several days to eat the control diet within a 2-hour period daily. On the day of killing, they were divided into three groups which consumed equal amounts of the control, imbalanced or corrected diets. One hour or 4 hours after eating the meal, the animals were killed and the polysome patterns in the livers were examined. Rats receiving the control and imbalanced diets showed similar polysome profiles, whereas animals receiving the corrected diet showed significantly more polysomes and fewer monosomes and disomes. This phenomenon was evident both with isoleucine and with threonine as the variable amino acid source. A second series of rats was fed ad libitum on the same control, imbalanced or corrected diets. At various times from 10 hours to 14 days after the start of the experiment, rats from each group were killed and the polysome profiles examined. At all times the polysome abundance was greatest for the rats on the corrected diets. These findings indicate that the polysome profiles in the liver of the rat can be influenced by dietary amino acids other than tryptophan, provided that a sufficiently severe amino acid deficiency can be created.