Biotransformation (Metabolism) of Pesticides - Pesticide Biotransformation and Disposition - page 78

associations between pesticides and susceptibility to various pesticide health effects
have provided information about the functional consequences of metabolism by
affected enzymes. A summary of some of the methods used to demonstrate XMEs in
in vitro studies is shown in Table 5.2 .
Biotransformation in the Liver
Pesticide absorption occurs through the skin as well as the respiratory and gastrointes-
tinal tracts, with eventual disposition to the liver from all routes of exposure, the liver
being the primary site of pesticide biotransformation for the purpose of facilitating
clearance through excretion of water-soluble products and detoxication. However, the

Table 5.2 In Vitro Tests for Microsomal Xenobiotic-Metabolizing Enzymes
Reaction or enzyme

Substrate Reference

Ester hydrolysis Methylthiobutyrate,

p -nitrophenyl acetate

Heymann and Mentlein (1981)

CYTOCHROME P450
1A1 rat Benzoapyrene Gelboin and Conney (1968); Denison

et al. (1983)

Ethoxyresorufin Aitio (1978); Burke and Mayer (1974);

Pohl and Fouts (1980)

1A2 rat Acetanilide Lewandowski et al. (1990); Mitoma and

Udenfriend (1962)

1A2 human Phenacetin Xenotech (2008)

2A6 Coumarin Xenotech (2008)

2B1/2 rat Pentoxyresorufin Lubet et al. (1985, 1990)

Benzphetamine Werringloer (1978)

Testosterone, 16a,16β-
hydroxylation

Sonderfan et al. (1987); Wood et al.
(1983)

2B6 human Buproprion Xenotech (2008)

2C8 human Amodiaquine Xenotech (2008)

2C9 human Diclofenac Xenotech (2008)

2C19 human Xenotech (2008)

2D6 human Dextromethorphan Xenotech (2008)

2E1 rat p -Nitrophenol Koop (1986)

2E1 Chloroxazone Xenotech (2008)

3A1 rat Testosterone, 6β-hydroxylation Li et al. (1995); Sonderfan et al. (1987)

3A4/5 human Testosterone 6,β-hydroxylation Xenotech (2008)

4A1 rat, human Lauric acid Kinsler et al. (1988); Xenotech (2008)

FLAVIN-CONTAINING MONOOXYGENASE
Phorate Levi and Hodgson (1988)

N,N -dimethylaniline Tynes and Hodgson (1985a,b)

Methimazole Dixit and Roche (1984)

Thiobenzamide Cashman and Hanzlik (1981)