Macromolecular synthesis in the isolated rat myointima in vitro

The myointima, which forms within the lumen of the carotid artery of the rat in response to the removal of the endothelium by a balloon catheter, could be extruded from the vessel as early as 6 days after denudation. The mean concentration of DNA in the isolated myointima increased as the myointima grew in vivo until 12 to 14 days after denudation, when the arterial lumen was filled with the myointima; thereafter the mean concentration of DNA declined. DNA and protein synthesis, incorporation of 3H-glucosamine and 3H-fucose into macromolecules, occurred in the myointima during incubation in vitro in the absence of fetal bovine serum, and with the exception of 3H-glucosamine, failed to be stimulated by it. These data indicate that the cells of the intact myointima do not require exogenous macromolecular growth factors for the synthesis of macromolecules in vitro.