Identification of human cytochrome P450 isozymes responsible for the in-vitro  oxidative demethylation of 4-methylaminoantipyrine

Salem Omran Ali Abdalla

doi:10.54361/

Authors

Salem Omran Ali Abdalla Department of Pharmacology, Faculty of Medicine, University of Tripoli, Tripoli, Libya Author

DOI:

https://doi.org/10.54361/

Keywords:

Metamizole, 4-methylaminoantipyrine, 4-aminoantipyrine (4-AA), metabolism, CYP2C19

Abstract

The aim of this study is to identify human cytochrome P-450 enzyme (CYP) mediating the oxidative N-demethylation of 4-methylaminoantipyrine (4-MAA) to 4-amino-antipyrine (4-AA). The contribution of human CYP to the metabolism of 4-MAA to 4-AA in human was investigated by using virus expressed human CYP, human liver microsomes and rat liver microsomes with chemical inhibition studies. The substrate of 4-methylaminantipyrine was employed at five different concentrations (12.5, 23, 46, 115 and 230 µmol/l) with varying concentrations of selective inhibitors of CYP (CYP1A2), (CYP3A4), (CYP2C8), (CYP2A6), (CYP2D6), (CYP2C19) and (CYP1A1). 4- MAA and 4-AA were analyzed by HPLC and enzyme kinetic parameters (Km and Vmax) were calculated from the concentration data. The transformation of 4-methylaminoantipyrine to 4- aminoantipyrine by microsomes prepared from baculovirus-expressed human CYP was pronounced with CYP2C19. Metabolism of 4-methylaminoantipyrine by human liver microsomes and rat liver microsomes was strongly inhibited by tranylcypromine, fluvoxamine and omeprazole inhibition was observed with other CYP selective inhibitors. 4-methyl-aminoantipyrine was also evaluated as a CYP substrate in rat liver microsomes. No significant inhibition of CYP1A2, CYP1A1, CYP3A4, CYP2C9, CYP2D6, CYP2A6 and CYP2E1 was observed in experiments (IC50 > 269.14 µM) but IC50 for CYP2C19 was 68.48 µM. In conclusion, the enzyme CYP2C19 apparently has an important role in N-demethylation of 4- methylaminoantipyrine.

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