Functional properties of rat liver protein synthesizing machinery in relation to aging

It is well established (van Bezooijen et al., 1977a) that the protein synthesis by isolated liver parenchymal cells (ILPC) from Wag/Rij rats is dependent in a characteristic way on the age of the donor. Whereas cells of middle-aged animals exhibit a decrease in proteo-synthesis activity under in vitro incubation conditions as compared to cells of young rats, a marked increase is observed between 24 and 36 months of age. To investigate whether this overall age-related variation is directly correlated with an intrinsic change at the level of the protein synthesis apparatus of hepatic cells, we compared the size distribution and the in vitro translational activity of polysomes from four age groups. We show that both exhibit the same biphasic response to aging as does the protein synthesizing capacity of ILPC.