The effects of estradiol and triiodothyronine on protein synthesis by hepatocytes of juvenile coho salmon (Oncorhynchus kisutch)

Abstract

A method was developed for studying the in vitro metabolism of radiolabeled amino acids by dispersed salmon hepatocytes. Radioactivity accumulated in trichloroacetic acid (TCA)-precipitable and -soluble fractions of cells and in TCA-precipitable fractions of incubation medium was measured. Estradiol (E2) or triiodothyronine (T3) stimulated the amount of radioactivity in the TCA-precipitable fraction of cells in a dose-dependent manner. T3 caused an increase in TCA-soluble radioactivity of cells that were incubated with [14C]serine, [14C]glycine or the nonmetabolizable amino acid [14C]cycloleucine. E2 had either no effect or caused a decrease in TCA-soluble radioactivity in cells that were incubated with [14C]serine or [14C]glycine. E2 increased TCA-soluble radioactivity in cells that were incubated with [14C]cycloleucine. E2 but not T3 caused an increase in TCA-precipitable radioactivity in the medium from incubation of hepatocytes with metabolizable radioactive amino acids. These results suggest that protein metabolism by salmon hepatocytes is stimulated by both E2 and T3 with differing kinetic patterns.