Testosterone 6P-hydroxylation

Figure 6 Correlation between testosterone 6P-hydroxylation and CYP3A protein levels, as determined by Western blot, in human hepatocytes incubated with several prototypical inducers.

A recent paper by Chauret et al. described the discovery of a novel fluorescent probe that is selectively metabolized by CYP3A in human liver microsomes (32). This probe, DFB [3-[(3,4-difhiorobenzyl)oxy]-5,5-dimethyl-4-[4-(methylsulfonyl) phenyl] furan-2(5F/)-one], is metabolized to DFH [3-hydroxy-5,5-dimethyl-4-[4-(methylsulfonyl)phenyl]furan-2(5//)-one], which has fluorescent characteristics (Fig. 7). In vitro CYP reaction phenotyping studies (cDNA-expressed CYP proteins and immunoinhibition experiments with highly selective anti-CYP3A4 antibodies) demonstrated that DFB was metabolized primarily by CYP3A4 (Fig. 8). Furthermore, metabolism studies performed with human liver microsomes obtained from different donors indicated that DFB dealkylation and testosterone 6P-hydroxylation correlated well (Fig. 9). 

Wang et al. (107) characterized the mechanism-based inhibition of testosterone 6p-hydroxylation (another CYP3A phenotypic marker) by verapamil enantiomers and each of their CYP3A metabolites—norverapamil and... 

Yamazaki, H., and Shimada, T. (1998). Comparative studies of in vitro inhibition of cytochrome P-450 3A4-dependent testosterone 6P-hydroxylation by roxithromycin and its metabolites, troleandomycin, and erythromycin. Drug Metab. Dispos. 26,1053-1057. 

Testosterone 6p-hydroxylation Testosterone 6 p-hydroxylation Testosterone 6 p-hydroxylation... 

Heterologous expression was achieved in bacteria but not any of several eukaryotic systems . The recombinant protein had only very low testosterone 6p-hydroxylation activity . 

Wang, R.W., D.J. Newton, T.D. Scheri, and A.Y.H. Lu (1997). Human cytochrome P450 3A4-catalyzed testosterone 6P-hydroxylation and erythromycin A -demethylation. Drug Metab. Dispos. 25, 502-507. 

Figure 4 Effects of OPZ, l,2-dithiole-3-thione (D3T), and OPZ M3 on CYP-catalyzed activities in Escherichia coli membranes. CYPl Al, 1A2, and IBl activities were estimated by 7-ethoxyresorufin 0-deethylation, CYP3A4 activity by testosterone 6p-hydroxylation, and CYP2E1 by chlorzoxazone 6-hydroxylation. (From Ref. 64.)...

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