title: N-alkylaminobenzotriazoles as isozyme-selective suicide inhibitors of rabbit pulmonary microsomal cytochrome P-450.
abstract: To produce potent, isozyme-selective suicide inhibitors of cytochrome P-450 (P-450), a series of N-alkylated 1-aminobenzotriazole (ABT) derivatives was synthesized; these included the N-methyl, N-butyl (BuBT), N-benzyl (BBT), and N-alpha-methylbenzyl (alpha MB) analogues of ABT. The suicide inhibitors showing the greatest potency and isozyme selectivity were BBT and alpha MB, compounds which included molecular features for P-450 inactivation (the ABT moiety) and similarity to benzphetamine. ABT and its N-alkylated derivatives were tested as suicide inhibitors in rabbit lung microsomes, whose P-450 monooxygenase system has been well characterized in both untreated and beta-naphthoflavone- or 2,3,7,8-tetrachlorodibenzo-p-dioxin-treated animals. ABT (10 mM) destroyed up to 99% of the total P-450 content of lung microsomes of untreated rabbits. At equimolar concentrations (10 microM), ABT was less effective than the N-alkylated compounds for the inhibition of P-450 isozyme 2-catalyzed benzphetamine N-demethylation (BND); in fact, BuBT, BBT, and alpha MB completely inhibited BND activity at this concentration and destroyed less than 40% of total pulmonary P-450. However, these compounds also inactivated 69-85% of isozyme 6-catalyzed 7-ethoxyresorufin O-deethylation. The most potent and isozyme-selective suicide inhibitor prepared was alpha MB: at 1 microM this compound inhibited approximately 80% of isozyme 2-catalyzed and 20% of isozyme 6-catalyzed monooxygenase activity but spared P-450 isozyme 5; at 2.5 microM it caused a near-complete loss (96 +/- 2%) of BND activity. The partition ratio of alpha MB, i.e., the molar ratio of inhibitor present to that of the P-450 destroyed, was 11 +/- 2, further demonstrating the potency of this compound. Experiments with BBT- and sodium phenobarbital-treated rats showed that the mechanism for suicidal inactivation of P-450 by this N-alkylated compound was by benzyne release, the same mechanism demonstrated earlier for the parent compound ABT.
mesh_terms: D000478:Alkylation; D000818:Animals; D001589:Benzphetamine / Q000378:metabolism; D065607:Cytochrome P-450 Enzyme Inhibitors; D007527:Isoenzymes / Q000037:antagonists & inhibitors*; D008168:Lung / Q000187:drug effects* / Q000378:metabolism; D008297:Male; D008861:Microsomes / Q000187:drug effects* / Q000378:metabolism; D009249:NADP / Q000378:metabolism; D010078:Oxazines / Q000378:metabolism; D010105:Oxygenases / Q000378:metabolism; D011817:Rabbits; D051381:Rats; D011919:Rats, Inbred Strains; D014230:Triazoles / Q000494:pharmacology*
chemical_list: D065607:Cytochrome P-450 Enzyme Inhibitors; D007527:Isoenzymes; D010078:Oxazines; D014230:Triazoles; D001589:Benzphetamine; C033020:1-aminobenzotriazole; D009249:NADP; C007649:ethoxyresorufin; D010105:Oxygenases