Relationship Between Protein Synthesis and Secretion in Liver Cells and the State of the Adenine Nucleotide System

Abstract

Adenine nucleotide levels could be precisely and reproducibly adjusted in liver cell suspensions by partially depleting the ATP pool with D-fructose or glycerol. Thus, it was possible to quantitatively correlate rates of protein synthesis and secretion with intracellular levels of ATP and with derived parameters, such as the adenylate energy charge. Half the maximum rate of incorporation of leucine into protein was observed at an energy charge of 0·80, a ratio of ATP to ADP of 2·6, and an ATP level of 1·05 pmol per g of wet cells. Proteins were secreted with half the maximum rate at an energy charge of 0·85, a ratio of ATP to ADP of 3·1 and an ATP concentration of 1 ·1 pmol per gof wet cells. Protein secretion dill not depend on continued synthesis. Inhibitors of oxidative phosphorylation inhibited protein secretion in addition to protein synthesis, in contrast to observations by other authors on liver slices.