Metabolism of the beta-carbolines, harmine and harmol, by liver microsomes from phenobarbitone- or 3-methylcholanthrene-treated mice. Identification and quantitation of two novel harmine metabolites.
This study extends an investigation of the metabolism of the beta-carbolines, harmine and harmol, by untreated, phenobarbitone-induced, or 3-methylcholanthrene (MC)-induced mouse liver microsomes to identify two MC-inducible metabolites of harmine and to quantitate their rates of formation using 3H-labeled substrate. An HPLC system was devised to separate harmine and its metabolites. The major metabolite with MC-induced microsomes was identified by mass spectroscopy and by NMR to be 6-hydroxy-7-methoxyharman and was produced at an initial reaction rate of 11 nmol/min/mg of microsomal protein (27-fold induction). The other novel metabolite, 3- or 4-hydroxy-7-methoxyharman (the position of the hydroxyl group could not be definitively assigned by NMR) was produced at an initial reaction rate of 3.8 nmol/min/mg of microsomal protein (32-fold induction) which was similar to the rate of formation of the other metabolite, harmol, determined previously. All three metabolites were further metabolized to unidentified metabolites. Protein binding of [3H]harmine and [3H]harmol was measured and shown to be metabolism dependent. It was also noted that the alkali conditions used for optimal extraction stimulated the protein binding.
D000470:Alkaloids / Q000378:metabolism*; D000818:Animals; D002851:Chromatography, High Pressure Liquid; D004790:Enzyme Induction / Q000187:drug effects; D006247:Harmine / Q000031:analogs & derivatives / Q000302:isolation & purification / Q000378:metabolism*; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D013058:Mass Spectrometry; D008748:Methylcholanthrene / Q000494:pharmacology; D051379:Mice; D008810:Mice, Inbred C57BL; D008862:Microsomes, Liver / Q000378:metabolism*; D010634:Phenobarbital / Q000494:pharmacology; D011485:Protein Binding
D000470:Alkaloids; C001326:harmol; D006247:Harmine; D008748:Methylcholanthrene; D010634:Phenobarbital