Effect of the reducing environment on the accumulation of elastin and collagen in cultured smooth-muscle cells.

We show here that cultured neonatal-rabbit aortic smooth-muscle cells produce and accumulate significant amounts of insoluble elastin. When grown in the presence of ascorbic acid, the amount of insoluble elastin in these cultures decreases, whereas the accumulation of collagen increases. These changes have been attributed to increased hydroxylation of proline in elastin. The function of ascorbic acid in proline hydroxylation is thought to be that of a reductive cofactor that maintains the proper oxidation state of molecular iron in the enzyme complex. This study shows that both ascorbic and isoascorbic acids act similarly to modify the accumulation of elastin and collagen in culture. On the other hand, cultures grown in the presence of dithiothreitol, a reducing agent previously shown to act as a cofactor for prolyl hydroxylase, do not demonstrate altered elastin accumulation. These studies are consistent with the suggestion that there is a specific role for ascorbic acid in this cellular system that cannot be replaced by other reducing cofactors.