The conversion of glucose into alanine and glutamic acid by rat liver, liver tumour and kidney in vivo

Abstract

Rats bearing liver tumors induced by-feeding p-dimethylaminoazobenzene were injected intravenously with a solution containing (C14) glucose and (C14) lysine. One hour after injection the animals were killed and soluble-protein fractions prepared from homogenates of the liver, liver tumor and kidney. The soluble-protein fractions from the tissues were treated with trichloroacetic acid (TCA). The protein precipitate was hydrolyzed, lysine, glutamic acid and alanine isolated and the radioactivity of these amino acids determined. Free lysine, glutamic acid and alanine present in the supernatants from TCA precipitates were isolated and their radioactivity determined. It is suggested that after the injection of a radioactive amino acid the ratio of the radioactivity of the free amino acid to that of the protein-bound amino acid in the tissue is a measure of the rate of synthesis of the proteins in the tissue. On this basis the rate of protein synthesis in the 3 tissues studied was, in descending order: kidney, liver, liver tumor. From a comparison of this ratio for glutamic acid and alanine compared with that of lysine it is concluded that the rate of formation of alanine from glucose is similar for liver and liver tumor, but a little lower for kidney; the rate of formation of glutamic acid from glucose in liver tumor is a little lower than that for liver, whereas for kidney it is much lower than for liver; the rate of formation of alanine from glucose in the 3 tissues is greater than the rate of formation of glutamic acid from glucose.