. Author manuscript; available in PMC: 2009 Dec 1.

Published in final edited form as: Chem Res Toxicol. 2008 Dec;21(12):2313–2323. doi: 10.1021/tx8002998

Table 1.

Inhibition of P450 1B1-mediated EROD activity by polycyclic aromatic inhibitors ^a

acetylenic inhibitors	inhibition of EROD activity		PAH inhibitors	inhibition of EROD activity
acetylenic inhibitors	mechanism*	IC₅₀ (μM)	PAH inhibitors	mechanism*	IC₅₀ (μM)
1EP	direct/restore	0.031 ± 0.004	B[a]A	direct/restore	0.009 ± 0.001
2EP	direct	0.110 ± 0.020	chrysene	direct	0.092 ± 0.011
4EP	direct/restore	0.250 ± 0.020	5MeCh	direct/restore	0.008 ± 0.001
1VP	direct/restore	0.088 ± 0.010	DMBA	direct/restore	0.300 ± 0.033
1PP	direct/restore	0.022 ± 0.003	B[a]P	direct/restore	0.031 ± 0.004
2EPh	direct	0.130 ± 0.021	B[e]P	direct/restore	0.017 ± 0.002
3EPh	direct/restore	0.110 ± 0.016	DB[a,j]Ac	direct/restore	0.015 ± 0.002
9EPh	direct	0.140 ± 0.018	3MC	direct	0.014 ± 0.002
2PPh	direct/restore	0.100 ± 0.012	FA	direct	0.015 ± 0.001
3PPh	direct/restore	0.040 ± 0.003	B[b]FA	direct/restore	0.005 ± 0.001
9PPh	direct	0.110 ± 0.021	B[j]FA	direct/restore	0.044 ± 0.006
2EN	direct	190 ± 16
4Ebi	direct	3.3 ± 0.5
4Pbi	mechanism-based	17 ± 2.0

“Direct” inhibitors are the chemicals that inhibited EROD activities throughout the incubation period and “direct/restore” inhibitors are the chemicals that inhibited EROD activities during the initial periods of incubation but for which EROD activity increased with increasing incubation time. 4Pbi is a mechanism-based inhibitor that required oxidation by P450 1B1 for the inhibition. IC₅₀ values were obtained at 15 s of incubation time for “direct” and “direct/restore” inhibitors and at 6 min of incubation time for the mechanism-based inhibitor. IC₅₀ values were determined with 5-7 concentrations of inhibitors and the results are presented as means and SE.