Changes in rat liver cytochrome P450 enzymes by atrazine and simazine treatment.
1. We examined the effect of two chloro-s-triazines (atrazine and simazine) on hepatic microsomal cytochrome P450 enzymes in rat. Rats were treated intraperitoneally with atrazine or simazine daily for 3 days with 100, 200 and 400 mumol/kg. 2. Among the P450-dependent monooxygenase activities, testosterone 2 alpha-hydroxylase (T2AH) activity in rat, which is associated with CYP2C11, was significantly decreased at all doses of atrazine and simazine. The levels relative to control activities were 59-46 and 60-32% respectively. Similarly, oestradiol 2-hydroxylase (ED2H) activity was also significantly decreased by 28-51% by atrazine and simazine at all doses. However, no change in CYP2C11 protein level by either chloro-s-triazine was observed. K(m) for T2AH was significantly increased only by simazine (200 mumol/kg), whereas the Vmax and Cl(int) for T2AH were significantly decreased by atrazine and simazine at all doses. 3. 7-Ethoxyresorufin O-deethylase (EROD), 7-methoxyresorufin O-demethylase (MROD) and 7-pentoxyresorufin O-depentylase (PROD) activities were significantly increased by 1.4-1.6-, 1.7-3.2- and 1.5-2.2-fold respectively, by both chloro-s-triazines at 200 or 400 mumol/kg. Lauric acid omega-hydroxylase (LAOH) was also increased by 1.4-fold by simazine at 200 and 400 mumol/kg. Immunoblotting showed that only simazine induces CYP1A2 and CYP4A1/2 protein expression. 4. The activities of 7-ethoxycoumarin O-deethylase (ECOD), bufuralol 1'-hydroxylase (BF1'H), chlorzoxazone 6-hydroxylase (CZ6H), testosterone 6 beta-hydroxylase (T6BH) and testosterone 7 alpha-hydroxylase (T7AH) were not affected by either chloro-s-triazine. 5. These results suggest that the pattern of changes in P450 isoforms by chloro-s-triazines differs between atrazine and simazine, that these herbicides change the constitutive and/or male specific P450 isoform(s) in rat liver, and that these changes closely relate to the toxicity of chloro-s-triazines.
Division of Environmental Chemistry, National Institute of Health Sciences, Tokyo, Japan.
N
N
Hanioka
H
H
Jinno
T
T
Tanaka-Kagawa
T
T
Nishimura
M
M
Ando
D000818:Animals; D001189:Aryl Hydrocarbon Hydroxylases; D001280:Atrazine / Q000494:pharmacology*; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism*; D000072467:Cytochrome P450 Family 2; D006540:Herbicides / Q000494:pharmacology*; D008297:Male; D008862:Microsomes, Liver / Q000187:drug effects* / Q000201:enzymology; D009929:Organ Size / Q000187:drug effects; D010105:Oxygenases / Q000378:metabolism; D011506:Proteins / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D012839:Simazine / Q000494:pharmacology*; D039181:Steroid 16-alpha-Hydroxylase; D013250:Steroid Hydroxylases / Q000378:metabolism
D006540:Herbicides; D011506:Proteins; D003577:Cytochrome P-450 Enzyme System; D010105:Oxygenases; D013250:Steroid Hydroxylases; D001189:Aryl Hydrocarbon Hydroxylases; C450279:CYP2C11 protein, rat; D000072467:Cytochrome P450 Family 2; D039181:Steroid 16-alpha-Hydroxylase; D001280:Atrazine; D012839:Simazine