RT Journal Article
SR Electronic
T1 Identification of Rat and Human Cytochrome P450 Isoforms and a Rat Serum Esterase That Metabolize the Pyrethroid Insecticides Deltamethrin and Esfenvalerate
JF Drug Metabolism and Disposition
JO Drug Metab Dispos
FD American Society for Pharmacology and Experimental Therapeutics
SP 1664
OP 1671
DO 10.1124/dmd.107.015388
VO 35
IS 9
A1 Stephen J. Godin
A1 J. Allen Crow
A1 Edward J. Scollon
A1 Michael F. Hughes
A1 Michael J. DeVito
A1 Matthew K. Ross
YR 2007
UL http://dmd.aspetjournals.org/content/35/9/1664.abstract
AB The metabolism of (αS)-cyano-3-phenoxybenzyl (1R, 3R)-cis-3-(2,2-dibromovinyl)-2,2-dimethylcyclopropane carboxylate (deltamethrin) and (αS)-cyano-3-phenoxybenzyl 2-(4-chlorophenyl)-3-methylbutyrate (esfenvalerate) by rat and human liver microsomes differs with respect to the biotransformation pathway (oxidation versus hydrolysis) responsible for their clearance. This study aims to further explore the species differences in the metabolism of these chemicals. Using a parent depletion approach, rat and human cytochromes P450 (P450s) were screened for their ability to eliminate deltamethrin or esfenvalerate during in vitro incubations. Rat P450 isoforms CYP1A1, CYP2C6, CYP2C11, and CYP3A2 and human P450 isoforms CYP2C8, CYP2C19, and CYP3A5 were capable of metabolizing either pyrethroid. Human CYP2C9 metabolized esfenvalerate but not deltamethrin. Rat and human P450s that metabolize esfenvalerate and deltamethrin do so with similar kinetics. In addition to the liver, a potential site of metabolic elimination of pyrethroids is the blood via serum carboxylesterase (CE) hydrolysis. The serum of rats, but not humans, contains significant quantities of CE. Deltamethrin and esfenvalerate were metabolized effectively by rat serum and a purified rat serum CE. In contrast, neither pyrethroid was metabolized by human serum or purified human serum esterases (acetylcholinesterase and butyrylcholinesterase). These studies suggest that the difference in rates of oxidative metabolism of pyrethroids by rat and human hepatic microsomes is dependent on the expression levels of individual P450 isoforms rather than their specific activity. Furthermore, these studies show that the metabolic elimination of deltamethrin and esfenvalerate in blood may be important to their disposition in rats but not in humans. The American Society for Pharmacology and Experimental Therapeutics