Regulation of protein synthesis in intact rat liver by calcium mobilizing agents.

1. Exposure of intact perfused rat liver to EGTA, vasopressin or phenylephrine resulted in a rapid decrease in polysome formation. Pretreatment with phentolamine, an alpha-adrenergic antagonist, blocked the effect of phenylephrine. 2. Hormonal inhibitions of leucine incorporation into protein in isolated hepatocytes and of polysome formation in perfused liver were reversed in the presence of supraphysiologic extracellular Ca2+ concentrations. 3. The beta-adrenergic agonist isoproterenol exerted minimal effects on polysome content. 4. It is proposed that intracellular Ca2+ stores sensitive to hormonal modulation are necessary for maintenance of protein synthesis in hepatocytes.