Intracellular localization and metabolism of the phenanthridinium trypanocide, ethidium bromide, by isolated rat hepatocytes

1. Confocal laser scanning microscopy (CLSM) has shown that ethidium (3,8-d iamino-5-ethyl-6-phenylphenanthridinium) bromide, an aromatic phenanthridin ium trypanocide, is taken up rapidly into the nucleoli and nuclear membrane s of isolated rat hepatocytes. 2. It is biotransformed by the hepatocytes and at least five metabolites ha ve been detected by high-performance liquid chromatography (HPLC). 3. Two new metabolites, 3- and 8-N-glucuronosylethidium, have been identifi ed by HPLC-electrospray mass spectrometry and they represent the major path way of metabolism, accounting for 6.4 +/- 0.7 and 19.5 +/- 1.2% respectivel y of total recovered drug after incubation. A third metabolite, 3,8-diacety lethidium, is formed in tract quantities. 4. The other two metabolites, 3-acetylethidium and 8-acetylethidium, have b een reported previously.