Differential inducing effect of benzo[a]pyrene on gene expression and enzyme activity of cytochromes P450 1A1 and 1A2 in Sprague-Dawley and Wistar rats.
The objective of this study was to compare RT-PCR, Western blot and determination of enzyme activity in the assessment of the induction of cytochromes P450 (CYPs) 1A1 and 1A2 by benzo[a]pyrene (BaP) in Sprague-Dawley and Wistar rats. Inhibition studies and kinetic analyses confirmed literature data indicating that methoxyresorufin is a specific CYP1A2 substrate in both uninduced and BaP-treated rats, whereas ethoxyresorufin is a specific CYP1A1 substrate only in BaP-treated rats. BaP treatment increased mRNA and protein expressions of both CYP1A enzymes to a greater extent in Wistar than Sprague-Dawley rats. It consistently caused a higher increase in mRNA and protein expression of the aryl hydrocarbon receptor in the former rats. By contrast, CYP1A2 enzyme activity was much more markedly increased in Sprague-Dawley than Wistar rats and CYP1A1 activity was induced to similar levels. A BaP-induced increase in the turnover number of CYP1A enzymes in Sprague-Dawley rats, relative to Wistar rats, may provide a plausible explanation for the differential effect of BaP on gene expression and enzyme activity. These results have methodological implications, since they show that RT-PCR and Western blot may not provide a quantitative measure of induction of CYP1A activity, which is the actual measure of the change in CYP1A-mediated metabolism.
Department of Pharmaceutical and Pharmacological Sciences, University of Padova, Padova, Italy.
Maura
M
Floreani
Daniela
D
Gabbia
Massimo
M
Barbierato
Sara
S
DE Martin
Pietro
P
Palatini
D000818:Animals; D001564:Benzo(a)pyrene / Q000494:pharmacology*; D019363:Cytochrome P-450 CYP1A1 / Q000096:biosynthesis / Q000235:genetics* / Q000378:metabolism*; D019388:Cytochrome P-450 CYP1A2; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics / Q000378:metabolism; D003580:Cytochromes / Q000096:biosynthesis / Q000235:genetics* / Q000378:metabolism*; D015870:Gene Expression / Q000187:drug effects; D007700:Kinetics; D008297:Male; D008862:Microsomes, Liver / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism; D010078:Oxazines / Q000494:pharmacology; D012333:RNA, Messenger / Q000235:genetics; D051381:Rats; D017207:Rats, Sprague-Dawley; D017208:Rats, Wistar; D018336:Receptors, Aryl Hydrocarbon / Q000235:genetics / Q000378:metabolism
D003580:Cytochromes; D010078:Oxazines; D012333:RNA, Messenger; D018336:Receptors, Aryl Hydrocarbon; D001564:Benzo(a)pyrene; C007649:ethoxyresorufin; D003577:Cytochrome P-450 Enzyme System; C076307:methoxyresorufin-O-demethylase; C017170:Cyp1a2 protein, rat; D019363:Cytochrome P-450 CYP1A1; D019388:Cytochrome P-450 CYP1A2