Effects of several pyrethroids on hepatic cytochrome P450 activities in rats.
Four commonly used pyrethroids (permethrin, bifenthrin, ethofenprox, and fenpropathrin) were orally administered to Sprague-Dawley rats for 5 days to study their effects on the liver cytochrome P450 (CYP) activities. Also Michaelis-Menten kinetics of the metabolic reactions catalyzed by liver CYPs were examined after adding these pyrethroids to the assay system to investigate their possible inhibitory effects on liver CYPs activities. These reactions included ethoxyresorufin O-deethylation, tolbutamide hydroxylation, bufuralol 1'-hydroxylation, and midazolam 4-hydroxylation, for CYP1A, 2C, 2D, and 3A activities, respectively. Results showed that oral administration of bifenthrin and ethofenprox highly induced CYP1A. The most potent inhibitors for CYP1A were fenpropathrin and cis-permethrin with K(i) values of 3.71 & 3.87 microM, respectively. CYP2D was slightly inhibited by both of fenpropathrin and cis-permethrin (K(i) values were 307.32 & 632.23 microM, respectively). On the other hand, none of CYP2C or 3A was inhibited by the tested pyrethroids. Since CYP1A may relate to biotransformation of many chemicals to reactive metabolites, bifenthrin and ethofenprox may potentiate mutagenicity of the chemicals through their inducing effects on CYP 1A. As permethrin and fenpropathrin were potent inhibitor for CYP1A, they may result in substantial accumulation of some chemicals. The resultant accumulation may lead to fatal toxicities in some case.
Abdou
Rania
R
Department of Veterinary Medicine, Faculty of Agriculture, Tokyo University of Agriculture and Technology.
Sasaki
Kazuaki
K
Khalil
Waleed
W
Shah
Syed
S
Murasawa
Youhei
Y
Shimoda
Minoru
M
D000284:Administration, Oral; D000818:Animals; D019363:Cytochrome P-450 CYP1A1 / Q000378:metabolism; D051544:Cytochrome P-450 CYP3A / Q000378:metabolism; D003577:Cytochrome P-450 Enzyme System / Q000187:drug effects / Q000378:metabolism*; D007700:Kinetics; D008297:Male; D008862:Microsomes, Liver / Q000201:enzymology*; D026023:Permethrin / Q000008:administration & dosage / Q000494:pharmacology; D011722:Pyrethrins / Q000008:administration & dosage / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013379:Substrate Specificity
D011722:Pyrethrins; C076840:ethofenprox; D026023:Permethrin; C099952:bifenthrin; C044267:fenpropathrin; D003577:Cytochrome P-450 Enzyme System; D019363:Cytochrome P-450 CYP1A1; D051544:Cytochrome P-450 CYP3A