Date of Award


Degree Type


Degree Name

Doctor of Philosophy


1-Aminobenzotriazole (ABT) and its N-benzyl (BBT), N-{dollar}\alpha{dollar}-methylbenzyl ({dollar}\alpha{dollar}MB), and N-{dollar}\alpha{dollar}-ethylbenzyl ({dollar}\alpha{dollar}EB) derivatives were compared for their potency and isozyme-selectivity for mechanism-based inactivation of guinea pig hepatic and pulmonary cytochrome P450 (P450) in vitro, through the use of isozyme selective substrates for the guinea pig orthologs of rabbit P450 2B4, 1A1, and 4B1 (P450 2Bx, 1A1, 4Bx, respectively). {dollar}\alpha{dollar}MB, {dollar}\alpha{dollar}EB, and to a lesser extent, BBT, selectively inactivated P450 2Bx in pulmonary microsomes from untreated or {dollar}\beta{dollar}-naphthoflavone ({dollar}\beta{dollar}NF)-induced, and hepatic microsomes from phenobarbital (PB)-induced, guinea pigs. P450 loss caused by ABT paralleled the inhibition of enzyme activity in hepatic and pulmonary microsomes; however, P450 loss caused by BBT, {dollar}\alpha{dollar}MB or {dollar}\alpha{dollar}EB was never greater than 45% even when monooxygenase activity was inhibited by virtually 100%. BBT, {dollar}\alpha{dollar}MB and {dollar}\alpha{dollar}EB were more potent inhibitors of P450 activity in hepatic and pulmonary microsomes from untreated compared to induced guinea pigs.;The NADPH-dependent metabolism, and covalent binding to protein, of ({dollar}\sp{lcub}14{rcub}{dollar}C) ABT,N-benzyl-1-amino- ({dollar}\sp{lcub}14{rcub}{dollar}C) 2,3-benzotriazole( ({dollar}\sp{lcub}14{rcub}{dollar}C) 2,3-BBT), and N- ({dollar}\sp{lcub}14{rcub}{dollar}C) 7-benzyl-1-aminobenzotriazole ( ({dollar}\sp{lcub}14{rcub}{dollar}C) 7-BBT), were examined in guinea pig hepatic or pulmonary microsomes. Hepatic microsomes from {dollar}\beta{dollar}NF (vs PB) treated guinea pigs metabolized ({dollar}\sp{lcub}14{rcub}{dollar}C) ABT, ({dollar}\sp{lcub}14{rcub}{dollar}C) 2,3-BBT or ({dollar}\sp{lcub}14{rcub}{dollar}C) 7-BBT more extensively and to more products. NADPH-dependent covalent binding to microsomal protein of ({dollar}\sp{lcub}14{rcub}{dollar}C) 2,3-BBT or ({dollar}\sp{lcub}14{rcub}{dollar}C) 7-BBT was greater than that of ({dollar}\sp{lcub}14{rcub}{dollar}C) ABT in hepatic microsomes, especially those from PB-induced animals, and the covalently modified proteins co-migrated with P450 2Bx on Western blots. Covalent binding per nmol P450 in pulmonary microsomes was 3- to 4-fold higher with ({dollar}\sp{lcub}14{rcub}{dollar}C) 2,3-BBT than with ({dollar}\sp{lcub}14{rcub}{dollar}C) 7-BBT or ({dollar}\sp{lcub}14{rcub}{dollar}C) ABT.; ({dollar}\sp{lcub}14{rcub}{dollar}C) BBT, at a dose which effectively inhibited pulmonary P450 2Bx, was rapidly metabolized and excreted by guinea pigs following i.v. administration, with 75% of the radiolabel excreted in the urine within 12 hr. By 48 hr, {dollar}<{dollar}1% of the radiolabel was present in liver, lungs, or kidneys of these animals.;In summary, BBT, {dollar}\alpha{dollar}MB, and {dollar}\alpha{dollar}EB are potent isozyme selective (P450 2Bx) inhibitors of guinea pig hepatic and pulmonary microsomal P450. BBT is metabolized in vitro to at least two reactive species capable of covalent modification of protein, and is rapidly ({dollar}<{dollar}12 hr) metabolized and excreted in vivo.



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