Inter-species comparisons of hepatic cytochrome P450 enzyme levels in male ruminants
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Our current knowledge about the biotransformation enzymes in wild ruminants is limited. The present study aimed to compare basic levels and specific activities of cytochrome P450 isoforms (CYP1A, 2A, 2B, 2C, 2D, 2E, 3A, 4A) in males of red deer (Cervus elaphus), fallow deer (Dama dama), roe deer (Capreolus capreolus) and mouflon (Ovis musimon). The proteins from the major cytochrome P450 (CYP) subfamilies were detected in all ruminant species by Western blotting, using polyclonal antibodies raised against rat or human CYP enzymes. The immunochemical data seem to suggest that humans and wild ruminants share some similar hepatic CYP enzymes corresponding to members of subfamilies 2 and 3; ruminant liver samples also contained two proteins cross-reacting with anti-rat CYP1A antibodies. High activities of CYP1A enzymes found in liver microsomes of male fallow deer and roe deer are indicative of increased susceptibility of these species towards promutagens that are metabolically activated by these CYPs. On the other hand, low activities of CYP1A-dependent alkoxyresorufin O-dealkylase activities were detected in male mouflons. Oxidative metabolism of testosterone was significantly higher in wild ruminants than the values previously reported from bulls. Androstene-3,17-dione and 6β-hydroxytestosterone were the most important products of testosterone oxidation in liver microsomes of all the ruminant species under study. The highest CYP3A-dependent testosterone 6β-hydroxylase activity was found in mouflons and fallow deer. A different pattern of CYP activities towards testosterone was found in roe deer, which showed high activities of testosterone 2β-hydroxylase and lower production of androstene-3,17-dione. An increased activity of CYP4A-dependent laurate 12-hydroxylase found in roe deer and mouflons might indicate a higher metabolic turnover of fatty acids. The data on CYP activities indicated that high metabolic rates of steroids, fatty acids, and xenobiotics may occur in male wild ruminants. The highest hepatic activities specific for CYP3A, CYP2C, CYP2D, and CYP2E enzymes were found in mouflon, suggesting that this species has the highest biotransformation capacity.
KeywordsCYPs Ruminants Immunoblotting Biotransformation
The authors wish to express their sincere thanks to Prof. F.P. Guengerich for his generous gifts (antisera against human CYPs, purified human CYP enzymes and expressing clones) and to Mrs. Eva Grobnerová and Marie Gájová (VRI, Brno) for their excellent technical assistance. This work was supported by the Grant Agency of the Czech Republic (grant no. 524/00/0514), Czech Ministry of Agriculture (grant no. QC0194) and the Grant Agency of Charles University (grant no. 96/2002/C/FaF). The authors hereby declare that the experiments comply with the current laws of the Czech Republic.
- Boobis AR, Sesardic D, Murray BP, Edwards RJ, Singleton AM, Rich KJ, Murray S, de la Torres R, Segura J, Pelkonen O, Pasanen M, Kobayashi S, Zhi-Guang T, Davies DS (1990) Species variation in the response of the cytochrome P-450-dependent monooxygenase system to inducers and inhibitors. Xenobiotica 20:1139–1161PubMedGoogle Scholar
- Fink-Gremmels J, Van Miert ASJPAM (1996) Species differences in biotransformation: conventional models in unconventional animal species. Exp Toxic Pathol 48(Suppl II):120–127Google Scholar
- Gillette JR (1971) Techniques for studying drug metabolism in vitro. In: La Du BN, Mandel HG, Way EL (eds) Fundamentals of drug metabolism and drug disposition. Williams and Wilkins, Baltimore, pp 400–418Google Scholar
- Guengerich FP (1995) Human cytochrome P450 enzymes. In: Ortiz de Montellano PR (ed) Cytochrome P450. Plenum Press, New York, pp 473–535Google Scholar
- Knodell RG, Hall SD, Wilkinson GR, Guengerich FP (1987) Hepatic metabolism of tolbutamide: characterization of the form of cytochrome P-450 involved in methyl hydroxylation and relationship to in vivo disposition. J Pharm Exp Ther 241:1112–1119Google Scholar
- Lewis DFV (2001) Guide to cytochromes P450. Structure and function. Taylor and Francis, LondonGoogle Scholar
- Weaver RJ, Thompson S, Smith G, Dickins M, Elcombe CR, Mayer RT, Burke MD (1994) A comparative study of constitutive and induced alkoxyresorufin O-dealkylation and individual cytochrome P450 forms in cynomolgus monkey (Macaca fascicularis), human, mouse, rat and hamster liver microsomes. Biochem Pharmacol 47:763–773CrossRefPubMedGoogle Scholar
- Yamazaki H, Guo Z, Persmark M, Mimura M, Inoue K, Guengerich FP, Shimada T (1994) Bufuralol hydroxylation by cytochrome P450 2D6 and 1A2 in human liver microsomes. Mol Pharmacol 16:568–577Google Scholar
- Zimniak P, Waxman DJ (1992) Liver cytochrome P450 metabolism of endogenous steroid hormones, bile acids, and fatty acids. In: Schenkman JB, Greim H (eds) Cytochrome P450. Springer, Berlin Heidelberg New York, pp 123–144Google Scholar