Age-dependent change in the ability of protein synthesis by rat liver microsomes-significance of 2 associated factors.

An activator and an inhibitor of polypeptide synthesis were isolated from microsomes of rat liver. The young rat contained a higher level of the activator but a lower level of the inhibitor than the aged rat. The significantly higher ratio of the specific activity of the activator to inhibitor in the young microsomes helps explain the higher capacity for protein synthesis of these microsomes as compared to the microsomes of the aged animal.