Interaction of ergotamine with liver Cytochrome P450 3A in rats

Ali S. Moubarak, Hehai Wang, Zelpha B. Johnson, Charles F. Rosenkrans

Department of Animal Science, University of Arkansas, Fayetteville, AR 72701.

DOI: 10.4236/as.2012.36096                

Abstract

This study was conducted to investigate the effect of the ergot alkaloid, ergotamine (ET), on the induction of CYP3A and the interaction in vivo and in vitro with ET. Sprague-Dawley rats were treated intraperitoneally for 4 days as follows: control (injecting with 0.5 ml of only corn oil); dexamethasone treatment (injecting with 100mg/kg of dexamethasone in corn oil); and ergotamine treatment (injecting with 100mg/kg of ergotamine in corn oil). Liver tissues were collected from each group (n = 5, total of 30 rats) and liver microsomes were prepared. Cytochrome CYP3A activity was evaluated using ET and its isomer as substrates in medium containing liver microsomes and NADPH at 37℃ for 30 min. HPLC was used to measure the disappearance of the substrate and the appearance of the metabolites. Liver microsomes from rats pretreated with dexamethasone were five times more (P < 0.01) active than microsomes from the control animals in the biotransformation of ET (32.1 and 7.0 nM/min/mg protein, respectively; SE = 4.83) or ET-isomer (21.6 and 4.7 nM/min/mg protein, respectively; SE = 1.7079) into its corresponding ET metabolites. The ergotamine treatment produced no increase (P > 0.05) in activity of CYP3A when compared to the control group (5.2 vs. 7.0 nM ET/min/mg protein; SE = 4.83) or ET isomer (1.5 vs. 4.7 nM ET isomer/ min/mg protein; SE = 1.70). When ketoconazole was used as specific inhibitor of CYP3A, ergotamine metabolisms were inhibited in a dose dependent fashion reaching a maximum at an inhibitor to substrate ratio of greater than one and LD50 at 0.5 nM of ketoconazole/mg protein. The data presented in this study suggest that although the ergot alkaloids ergotamine and its isomer are ideal substrates for the isozyme CYP3A, these compounds have no effect on the induction of CYP3A after 4 days of treatment.

Keywords

Microsomes; Liver; Rat

Conflicts of Interest

The authors declare no conflicts of interest.

References

[1]	Porter, T.D., and Coon, M.J. Cytochrome P-450. (1991) Multiplicity of isoforms, substrates, and catalytic and regulatory mechanisms. J. Biol. Chem. 266:13469-13472.
[2]	Brosen, K. (1993) The pharmacogenetics of the selective serotonin reuptake inhibitors. Clin. Investig. 71: 1002-1009.
[3]	Pollock, B.G. (1994) Recent developments in drug metabolism of relevance to psychiatrists. Harv. Rev. Psychiatry 2:204-213.
[4]	DeVane, C.L. (1994). Pharmacokinetics of the newer antidepressants: clinical relevance. Am. J. Med. 97:13S-23S.
[5]	Wright, M.C., and Paine, A.J. (1994) Induction of the cytochrome P450 3A subfamily in rat liver correlates with the binding of inducers to a microsomal protein. Biochem Biophys. Res. Commun. 201:973-979.
[6]	Ball, S.E., Maurer, G., Zollinger, M., Ladona, M., and Vickers, A.E. (1992) Characterization of the cytochrome P-450 gene family responsible for the N-dealkylation of the ergot alkaloid CQA 206-291 in humans. Drug Metab. Dispos. 20:56-63.
[7]	Moochhala, S.M., Lee, E.J., Hu, G.T., Koh, O.S., and Becket, G. (1989) Effects of bromocriptine on hepatic cytochrome P-450 monooxygenase system. Jpn. J. Pharmacol. 49:285-291.
[8]	Thummel, K.E., and Wilkinson, G.R. (1998) In vitro and in vivo drug interactions involving human CYP3A. Annu Rev Pharmacol Toxicol. 38:389-430; 1998.
[9]	Witkamp, R.F., Nijmeijer, S.M., Monshouwer, M., and Van Miert, A. S. (1995) The antibiotic tiamulin is a potent inducer and inhibitor of cytochrome P4503A via the formation of a stable metabolic intermediate complex. Studies in primary hepatocyte cultures and liver microsomes of the pig. Drug Metab. Dispos. 23(5):542 547.
[10]	Lehmann, J. M., McKee, D.D., Watson, M.A., Willson, T.M., Moore, J.T., and Kliewer, S.A. (1998) The human orphan nuclear receptor PXR is activated by compounds that regulate CYP3A4 gene expression and cause drug interactions. J. Clin. Invest. 102:1016-102.
[11]	Moore, L.B., Parks, D.J., Jones, S.A., Bledsoe, R.K., Consler, T.G., Stimmel, J.B., Goodwin, B., and Liddle, C., Blanchard, S.G., Willson, T.M., Collins, J.L., Kliewer, S.A. (2000) Orphan nuclear receptors constitutive androstane receptor and pregnane X receptor share xenobiotic and steroid ligands. J. Biol. Chem. 275:15122-15127.
[12]	Sueyoshi, T., Kawamoto, T., Zelko, I., Honkakoski, P., and Negishi, M. (1999) The repressed nuclear receptor CAR responds to phenobarbital in activating the human CYP2B6 gene. J. Biol. Chem. 274:6043-6046.
[13]	Pascussi, J.M., Drocourt, L., Fabre, J.M., Maurel, P., and Vilarem, M.J (2000). Dexamethasone induces pregnane X receptor and retinoid X receptor-alpha expression in human hepatocytes: synergistic increase of CYP3A4 induction by pregnane X receptor activators. Mol. Pharmacol. 58:361-372.
[14]	Honkakoski, P., and Negishi, M. (2000) Regulation of cytochrome P450 (CYP) genes by nuclear receptors. Biochem. J. 347:321-337.
[15]	Moubarak, A.S., and Rosenkrans, C.F., Jr. (2000) Hepatic metabolism of ergot alka-loids in beef cattle by cytochrome P450. Biochem. Biophys. Res. Commun. 274:746-749.
[16]	Lowry, O.H., Rosebrough, N.J ., Farr, A.L., and Randall, R.J.J. (1951) Protein Measurements with Folinphenol Reagent. Biol. Chem. 193:265-275.
[17]	Moubarak, A.S., Rosenkrans, C.F. Jr., and Johnson, Z.B. (2003) Modulation of cytochrome P450 meta-bolism by ergonovine and dihydroergotamine. Vet Hum Toxicol. 45:6-9.
[18]	Lampen, A., Christians, U., Guengerich, F P., Watkins, P.B., Kolars, J C., Bader, A., Gonschior, A.K., Dralle, H., Hackbarth, I., and Sewing, K.F. (1995) Metabolism of the immunosuppressant tacrolimus in the small intestine: cytochrome P450, drug interactions, and interindividual variability. Drug Metab Dispos 23:1315-1324.
[19]	Christians, U., Schmidt, G., Bader, A., Lampen, A., Schottmann, R., Linck, A., and Sewing, K F. (1996) Identification of drugs inhibiting the in vitro metabolism of tacrolimus by human liver microsomes. Br J Clin Pharmacol 41:187-190.
[20]	Althaus, M., Retzow, A., Castell, J V., Gomez-Lechon, M.J., Amalou, Z., Rose, T., and Appel, K. (2000) In vitro identification of the cytochrome P450 isoform responsible for the metabolism of alpha-dihydroergocryptine. Xenobiotica 30:1033-1045.