The effect of diphenylhydantoin on fibroblasts in vitro.

It was found that 0.02 mM was the higher concentration of drug which is not toxic and is compatible with normal cell morphology and growth over a period of a week. Using this concentration of drug there was no consistent stimulation of cell growth. A small increase in cell number was noted, however, in some cultures during the first 24 hours of culture. DpH at a concentration of 0.02 mM in the presence of ascorbic acid decreased collagen prolyl hydroxylation in "old" W1-38 cultures but a concentration of 0.1 mM was required to decrease the values to a similar extent in "young" cultures. A concentration of 0.02 mM DpH had no effect on hydroxylation in an "old" HGF culture. It is speculated that in a responsive individual a reduction of collagen prolyl hydroxylation may play a role in the etiology of DpH-induced gingival enlargement and congenital malformations.