Patterns of albumin and general protein synthesis in rat liver as revealed by gel electrophoresis

Abstract

Patterns of protein synthesis in rat liver microsomal fractions have been studied using polyacrylamide gel electrophoresis. In vivo patterns were obtained after injecting rats with 14C-labelled amino acids, and sacrificing them 20 min later. The livers were fractionated by standard techniques. Synthesis of albumin by the liver microsomes was found to be somewhat reduced relative to other proteins, 18–20 h after partial hepatectomy. In vitro patterns were obtained by incubating subcellular fractions with 14C-labelled amino acids, GTP and an ATP-generating system, and examining the sonic extract of the incorporation mixture. Extracts from regenerating livers again made less albumin relative to other proteins than did normal extracts. In vivo-like patterns were obtained using the 500 × g, 3000 × g, 15 000 × g supernatants, and microsomes with microsomal supernatant. Integrity of the pattern was lost upon dilution of the microsomal supernatant or when polysomes were used with whole supernatant. The major peak in the patterns co-electrophoresed slightly behind rat serum albumin and was identified as albumin by chemical and immunological means.