Table 2

Correlation of various CYP isoform catalytic activities with methoxychlor mono-O-demethylation in a panel of human liver microsomes

Activity^2-a	P450 Isoforms Involved	Adjusted R² Value Determined by Univariate Linear Regression
Activity^2-a	P450 Isoforms Involved	1 μM methoxychlor	25 μM methoxychlor
Total P450		0.19	0.22^2-150
Cytochromec reductase		−0.09	−0.06
EthoxycoumarinO-deethylase	Multiple	−0.04	−0.05
Phenacetin O-deethylase	CYP1A2	0.54**	0.33^2-150
Coumarin 7-hydroxylase	CYP2A6	0.00	−0.03
Mephenytoin 4′-hydroxylase	CYP2C19	0.79***	0.52***
DextromethorphanO-demethylase	CYP2D6	−0.07	0.01
Chlorzoxazone 6-hydroxylase	CYP2E1	−0.09	−0.07
Testosterone 6β-hydroxylase	CYP3A4	−0.09	−0.04
Lauric acid ω-hydroxylase	CYP4A	−0.09	−0.05
		AdjustedR ² value determined by multivariate linear regression
Mephenytoin 4′-hydroxylase/	CYP2C19/	0.96^2-b	0.65^2-c
Phenacetin O-deethylase/	CYP1A2/
Coumarin 7-hydroxylase	CYP2A6

↵2-150 , indicates statistical significance, p < 0.05. **, indicates statistical significance, p < 0.01. ***, indicates statistical significance, p < 0.001.
↵2-a Isoform-specific catalytic activities were measured by the vendor (IIAM, Exton, PA). Mono-O-demethylation of methoxychlor was measured as described in the materials and methods in 13 and 16 livers using 1 and 25 μm methoxychlor, respectively.
↵2-b The model was significant overall, p < 0.001. CYP2C19, CYP2A6, and CYP1A2 marker activities made a significant contribution, with p values of <0.001, <0.001, and <0.05, respectively.
↵2-c The model was significant overall, p < 0.001. CYP2C19, but not CYP2A6 or CYP1A2 marker activities made a significant contribution, with p values of <0.01, orp = 0.055 and 0.161, respectively.