Early effects of refeeding a complete diet on the translational initiation activity in rat liver slices

A complete diet containing 23% protein was fed to two-day-fasted rats. The effects of this diet on protein biosynthesis, through the examination of liver slices, was investigated. (1) Refeeding enhanced the protein-synthesizing activity with better preservation of heavy polysomes in the liver slices. Protein in the diet was necessary to induce, through refeeding, the activation of protein synthesis in the liver. (2) The incorporation of [3H]methionine into 40S subunits and 80S subunits, where "run-off" 40S and 60S subunits had been accumulated by preincubation with 2 x 10(-6) M pactamycin, was much higher in the liver slices of refed rats than in the liver slices of fasted rats. By using chain initiation inhibitors, it was shown that labeled 40S and 80S subunits were 40S and 80S initiation complexes, respectively.