Studies on amino acid incorporation in isolated toad bladder epithelial cells. Seasonal changes in protein synthesis

Abstract Amino acid incorporation in isolated toad bladder epithelial cells was investigated by examining the rate of radiolabel incorporation into trichloroacetic acid-insoluble material. The results demonstrated that during the summer months, a large fraction of the radiolabel incorporated was not inhibited by cycloheximide and did not seem to correspond to incorporation of the radioactive amino acid into elongating peptides. A similar effect was not observed in other organs of the toad (e.g. liver, spleen). During the winter months, however, virtually all the acid-insoluble radiolabel appears to correspond to incorporation of the amino acid into elongating peptides. Ouabain, an inhibitor of sodium transport, inhibited amino acid incorporation into acid-insoluble material by affecting the acid-soluble pool and this effect appeared to be independent of the effect of ouabain on sodium transport. The isolated epithelial cells appeared to derive the energy for protein synthesis almost entirely from glycolysis and in this regard they resemble certain tissue culture cells.