Back to the Top
Dear reader,
We are looking for an index reaction to determine the activity of
cytochrome P450 isoform 3A3/4 in human liver microsomes (in vitro).
Currently we used dextromethorfan N-demethylase as index reaction for
CYP3A4. However, a current article suggests that also CYP2E1 is
involved in the formation of 3-methoxymorphinan and therefore
dextromethorfan N-demethylase is not a good index reaction.
Does anybody have a GOOD suggestion how to determine the CYP3A4
activity in vitro ?
Greetings
Alex Hemeryck and Liping Pan, Ph D students.
__________________________________
Alex Hemeryck
Pharmacist
Heymans Institute of Pharmacology
University of Ghent
Medical School
De Pintelaan 185
B-9000 Ghent
Tel: +32-9-2403370
Fax: +32-9-2404988
e-mail: Alex.Hemeryck.aaa.rug.ac.be
__________________________________
Back to the Top
Hydroxylation of testosterone to 6-hydroxytestosterone is commonly used as
an index reaction for CYP3A4/5 in human liver microsomes. Also, recently it
has been reported that alprazolam 4-hydroxylation is predominantly
metabolized by CYP3A3/4. Erythromycin N-demethylation and midazolam
hydroxylation are other common probe reactions. Nipedipine is another
substrate for CYP3A4. Following references might give more information.
Alprazolam metabolism in vitro: studies of human, monkey, mouse and rat
liver microsomes, von Moltke, LL, Greenblatt, DJ, Harmatz, JS, Shader, RI;
Pharmacology, 1993, 47, 268-276
Characterization of six in vitro reactions mediated by human cytochrome
P450: Application to the testing of cytochrome P450-directed antibodies,
schmider, J.; Greenblatt DJ, von Moltke, LL; Harmatz JS, Duan Sx, Karsov D,
Shader RI, Pharmacology, 1996, 52, 125-134
Cytochrome P450 isoform inhibitors as a tool for the investigation of
metabolic reactions catalyzed by human liver microsomes, Bourrie M, Meunier
V, Berger Y, Fabre G, J. Pharm. Exp. Ther. 1996, 277, 321-332
Also, you can get some information at the Glaxo Wellcome drug metabolism
guide on the web at http://www.glaxowellcome.co.uk/science/drugmet/index.html
Hope this helps.
Chandrani Gunaratna
Chandrani Gunaratna, Ph.D.
Senior Research Chemist
Bioanalytical Systems
2701 Kent Avenue
West Lafayette, IN 47906
Phone: (765)463-4527
E-Mail: prema.aaa.bioanalytical.com
Back to the Top
I think you should read the article of Buening et al. "Activation and
inhibition of benzo(a)pyrene and aflatoxine B1 metabolism in human
liver microsomes ....." Cancer research 1981 41: 67-72
Or maybe the article of de Waiziers et al. "Cytochrome P450
isoenzymes, epoxide hydrolase and glutathion transferase in rat and
human hepatic and extrahepatic tissues"
J Pharmacol Exp Ther 1990 253: 387-394
As far as I know the Cytochrome P450 IIIA4 activity is correlated
well with the Erythromycindemethylase (ED) activity (r=0.84,
p=0.001).
In addition the midazolam hydroxylation activity was used to measure
the Cyt P450 IIIA4 activity.
Hope these information will be helpful
Regards,
Ralph Quadflieg, Pharm D
Department of Pharmaceutical Technology and Biopharmacy
Universtity of Bonn
An der Immenburg 4
D-53121 Bonn
Germany
Phone: ++49 228 73-5117
Fax: ++49 228 73-5268
PharmPK Discussion List Archive Index page
Copyright 1995-2010 David W. A. Bourne (david@boomer.org)