Enhanced synthesis of collagen and total protein by smooth muscle cells from atherosclerotic rabbit aortas in culture.

Protein synthesis in smooth muscle cells from normal and atherosclerotic rabbit aortas was studied. Cultures of cells from the third passage were incubated with [3H]proline and the synthesis rates of collagen and total protein measured from the radioactivities incorporated into protein-bound hydroxyproline and proline, respectively. The synthesis ratio of collagen types I and III was studied by separating the radioactive procollagens of the culture media by DEAE column chromatography. The synthesis rates of both collagen and total protein were higher in cells cultured from atherosclerotic rabbit aortas. There was no difference in the synthesis ratios of types I and III collagen between cells from the two origins. In addition to procollagens, a third protein eluted before procollagen I in the DEAE chromatography of medium proteins. Compared with control cells, cells from atherosclerotic aortas incorporated relatively less radioactivity into this protein. No differences were detected in the amino acid compositions of cellular proteins between cells from both origins. It was concluded that cells grown from atherosclerotic rabbit aortas synthesize more collagen and total protein than those from normal aortas, the synthesis of collagens I and III being equally enhanced. The results also suggest that there are proteins which are not involved in the general enhancement of protein synthesis.