beta-Carbolines as selective monoamine oxidase inhibitors: in vivo implications.
The inhibitory action of a range of beta-carbolines on human and rat monoamine oxidase (MAO) A and B has been studied. Concentrations of 5-hydroxytryptamine and phenylethylamine, approximately at their Km values, were used as substrates for MAO A and B respectively. A wide variation in selectivity was found, with harmaline being 10,000 times more potent an inhibitor of A than B whereas, using tetrahydro-beta-carboline and harmane, the difference was nearer to ten-fold. Of the carbolines which have been found endogenously, tetrahydro-beta-carboline, 6-methoxytetrahydro-beta-carboline and harmane are all sufficiently potent inhibitors of human MAO A, with I50 values of 5 X 10(-6), 10(-6), 5 X 10(-7) M respectively, for this property to be of possible physiological significance. Harmane, with an I50 of 5 X 10(-6) M, might also play a role as an inhibitor of MAO B.
D000818:Animals; D001792:Blood Platelets / Q000201:enzymology; D002243:Carbolines / Q000494:pharmacology*; D005260:Female; D006801:Humans; D007211:Indoles / Q000494:pharmacology*; D008099:Liver / Q000201:enzymology; D008995:Monoamine Oxidase; D008996:Monoamine Oxidase Inhibitors; D010920:Placenta / Q000201:enzymology; D011247:Pregnancy; D051381:Rats
D002243:Carbolines; D007211:Indoles; D008996:Monoamine Oxidase Inhibitors; D008995:Monoamine Oxidase