Collagen synthesis in cultured human skin fibroblasts: effect of ascorbic acid and its analogs.

In confluent human skin fibroblasts maintained in 0.5% serum-supplemented medium. L-ascorbate specifically stimulated the rate of incorporation of labeled proline into total collagenase-sensitive protein, without changing the specific activity of the intracellular free proline. This influence of ascorbate reached a maximum at 30 microM and continued for at least 4 days, resulting in a 4-fold increase. The ascorbate effect occurred in cells at both confluent and subconfluent densities and was evident at all serum concentrations from 0.5-20%. The effect was independent of duration of the radioactive pulse between 2-6 h. D-Ascorbate, D-isoascorbate, and L-dehydroascorbate also stimulated collagen synthesis but at considerably higher concentrations, i.e., 250-300 microM. The stimulation of collagen synthesis by ascorbate and its analogs was accompanied by a decline in prolyl hydroxylase activity and a rise in lysyl hydroxylase activity; again L-ascorbate was found to be most effective. Dimethyltetrahydropterine and L-lactate failed to produce these effects.