Effect of phenytoin on intracellular 45Ca2+ accumulation in gingival fibroblasts in vitro

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Abstract
Effect of 5,5 diphenylhydantoin (phenytoin; PHT) alone or in combination with epidermal growth factor (EOF) on the intracellular accumulation of the radio–isotope 45Ca2+ (4 min labelling period) was determined in gingival fibroblasts. EOF as well as PHT increased the intracellular accumulation of the radioisotope in normal gingival fibroblasts by approximately 2 and 1.6-fold, respectively. In contrast, in fibroblasts derived from the phenytoin–induced gingival overgrowth, neither EGF nor PHT stimulated intracellular accumulation of 45Ca2+. When normal gingival fibroblasts were treated in vitro with EGF in combination with PHT, the EGF-induced increase in intracellular accumulation of the radioisotope 45Ca2+ was abolished. The rate of efflux of the radioisotope 45Ca2+ in prelabelled normal gingival fibroblasts was decreased by PHT treatment in vitro to a level already present in fibroblasts derived from PHT–induced gingival overgrowth. This study indicates that PHT influences the cellular calcium metabolism in fibroblasts which may contribute to the pathogenesis of gingival overgrowth.