Influence of age on the synthesis of macromolecules in the smooth muscle cells of the isolated myointimal mass in vitro.

The influence of growth and aging on the synthesis of DNA, RNA and protein in the myointima in vivo was explored by incubating isolated myointima of different ages in labelled precursors. As myointima grew and aged in vivo, the rates of DNA and protein synthesis declined, while the quantity of DNA increased more than two-fold in seven days. The rate of RNA synthesis remained constant and was unaffected by growth. Like that of DNA and protein synthesis, fetal bovine serum was not required by the isolated myointima to synthesize RNA in vitro. Taken together, these findings confirm and extend our previous results which showed the synthetic autonomy of the isolated myointima, and demonstrate further that during growth the synthesis of RNA is affected in a manner that differs from that which controls DNA and protein.