Studies on the binding of 5,5-diphenyl-hydantoin to nucleic acids in vitro and to rat brain subcellular fractions in vitro and in vivo. 
The binding of 5,5-diphenylhydantoin (DPH) to nucleic acids (bovine brain RNA, rat liver ribosomal and tRNA, Torula utilis RNA, and calf thymus and Escherichia coli DNA was studied using ultraviolet spectroscopy, gel chromatography and thermal transition profiles.  Within the sensitivity of these methods, it was found that there is essentially little or no interaction between DPH and nucleic acids in vitro as has been reported previously.  Little, if any evidence of DPH intercalation with DNA was noted during thermal transition studies.  DPH does not interfere with DNA reassociation.  Further studies into the nature of the in vivo subcellular distribution of 14C-DPH in rat brain revealed accumulation of the radioactivity primarily in the soluble fractions.  The nuclear fraction and the microsomes, containing high DNA and RNA tissue ratios, demonstrated the greatest particulate association with radioactivity at 2 and 12 hours, respectively.  This association with particulate fractions was not demonstrated after gel chromatography.  These data do not support a hypothesis relating DPH binding to nucleic acids in vitro or in vivo to a possible mechanism of action of the drug.