Amino Acid Composition of Morphological Fractions of Rat Livers and Induced Liver Tumors. ∗

Abstract

Summary

1. The perfused livers from adult rats fed either a basal diet containing 12% of casein or the same diet plus 4-dimethylaminoazobenzene for 4 weeks, and the liver tumors induced by this dye were fractionated into nuclear, large granule (mitochondria), small granule (microsome), and supernatant fluid fractions. The amounts of 17 amino acids were determined in the total proteins from the original homogenate and in each of the fractions. The importance of using perfused livers for these analyses was demonstrated experimentally.

2. When the basal diet was fed, the proteins from the nuclear fraction contained lower concentrations of histidine, tryptophan, phenylalanine, and cystine and a higher concentration of glycine than the whole liver proteins. The large granule proteins contained less histidine, the small granule proteins less methionine and glycine and more tryptophan, and the supernatant fluid proteins less tryptophan and more cystine than the proteins of the original homogenate.

3. The livers of rats fed the dye contained higher concentrations of glutamic acid in the nuclear proteins, arginine in the large granule proteins, and cystine and tryptophan in the supernatant fluid proteins than normal livers.

4. The proteins from each fraction of liver tumor contained less methionine and more cystine than the proteins in the corresponding