BIS-BENZIMIDAZOLE DYES, HOECHST-33258 AND HOECHST-33342 - RADIOIODINATION, FACILE PURIFICATION AND SUBCELLULAR-DISTRIBUTION

A simple HPLC method is presented for the purification of DNA binding bis-benzimidazole dyes Hoechst 33258, Hoechst 33342 and I-131-iodoHoec hst 33258. The mobile phase, consisting of methanol and aqueous ammoni a (0.2%) in the ratio 2:3, resolved and separated the radiochemical fr om unlabeled ligand and other reagents used in the reaction, thereby r esulting in high radiochemical purity and yield. The iodinated Hoechst 33258 did not show any selective binding to nuclear DNA when cell fra ctionation studies were performed with cultured mammalian cells as wel l as in mice testes. Fluorescence microscopy studies with V79 cells st ained with these dyes, showed the superiority of Hoechst 33342 in sele ctive localization in nuclear DNA compared to Hoechst 33258. The diffe rence in behavior of these two dyes in terms of binding to nuclear DNA , and hence their ability to provide protection against damage caused by ionizing radiation, may be explained on the basis of the molecular charge. The high chemotoxicity of Hoechst 33342 observed in the presen t studies suggests that its usefulness as a radioprotector against chr onic irradiation of tissue by incorporated radionuclides may be limite d.