Differences in growth response to hydrocortisone and ascorbic acid by human diploid fibroblasts

The effects of hydrocortisone and ascorbic acid on growth parameters were measured in human diploid skin fibroblasts from fetal and adult donors. In the presence of culture medium containing 10% fetal bovine serum, 0.3 micrometer hydrocortisone produced a 20% increase in the population growth rate and a 50 to 70% increase in the confluent density of fibroblasts from adult donors. Daily addition of 28 micrometer ascorbic acid also stimulated the population growth rate and cell density at confluency. The effects of hydrocortisone and ascorbic acid on the final cell density were additive. The action of hydrocortisone was restricted to cells in log-phase growth, whereas ascorbic acid affected cells in both the log and the post-confluent phases of the growth cycle. In fibroblasts from fetal donors, ascorbic acid was stimulative but hydrocortisone was not. The data suggest that whereas both compounds stimulate cell growth in an additive manner, they do so by different cellular mechanisms.