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Dear All,
I'm new to this discussion group, but already found it extremely
helpful...
I have two questions:
1. I found a major (M+16) metabolite in rat bile (in BDC rats after PO
dosing) but not present in rat liver mics or rat (or other species)
hepatocyte incubations. It's likely just a terminal phenyl ring
oxidation - if I have to guess, I would say maybe by CYP3A. Has
anyone seen this before? This cmpd is not a CYP inhibitor. How can I
try to see the metabolite in vitro? I could not see any metabolite
formation in RLM, HLM etc. In hepatocytes, I only saw N-oxide
formation which is a minor one in bile. Is it possible that the major
metabolite was generated in vivo by gut metabolism, or metabolism from
sinusoidal endothelial cells (SEC), Kupper cells, hepatic stellate
cells or bile duct?
Response(s) are very appreciated. Thanks.
Yang
--
Yang Xu, Ph.D.
Scientist
Pharmacokinetics and Drug Metabolism
Amgen Inc.
One Amgen Center Drive, MS 30E-2-C
Thousand Oaks, CA 91320-1799
Back to the Top
Dear All,
I'm new to this discussion group, but already found it extremely
helpful...
I have two questions:
1. I found a major (M+16) metabolite in rat bile (in BDC rats after PO
dosing) but not present in rat liver mics or rat (or other species)
hepatocyte incubations. It's likely just a terminal phenyl ring
oxidation - if I have to guess, I would say maybe by CYP3A. Has
anyone seen this before? This cmpd is not a CYP inhibitor. How can I
try to see the metabolite in vitro? I could not see any metabolite
formation in RLM, HLM etc. In hepatocytes, I only saw N-oxide
formation which is a minor one in bile. Is it possible that the major
metabolite was generated in vivo by gut metabolism, or metabolism from
sinusoidal endothelial cells (SEC), Kupper cells, hepatic stellate
cells or bile duct?
Response(s) are very appreciated. Thanks.
Yang
--
Yang Xu, Ph.D.
Scientist
Pharmacokinetics and Drug Metabolism
Amgen Inc.
One Amgen Center Drive, MS 30E-2-C
Thousand Oaks, CA 91320-1799
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The following message was posted to: PharmPK
Dear Yang, in which culture mode did you use your rat hepatocytes? The
suspension mode is perhaps not the best one because too short term for
terminal metabolism, you may consider the monolayer culture mode as more
appropriate. You can also try the slice model where all cell types are
present if you have reasons to believe your M+16 metabolite is not
produced
by the hepatocytes (?). This model is now commercially available in the
frozen format, ie ready to use.
Christophe Chesne
Biopredic international
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The following message was posted to: PharmPK
Dear Christophe,
We used hepatocyte suspension for 2 hr incubation! Thanks for your
suggestions! I like them - I am going to try both monolayer culture
and other cell types in liver. What's intriguing was that for other
structurally similar cmpds, hepatocyte suspension worked well in
producing those terminal M+16 metabolites!
I'll let you know how this works.
Yang
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Hi Yung,
It is evident form your query that you are still uncertain about the
enzyme/enzyme system responsible for its formation. I reckon its worth
doing the above in vivo study in 1-aminobenzotriazole (suicidal CYP
450 inhibitor) predosed rats. According to your theory, if its the
terminal phenyl ring oxidation product which is formed by CYP 450,
then you should notice a decrease in its formation in 1-
aminobenzotriazole treated rats.
As you are unable to see this metabolite in RLM and hepatocytes, I
suggest you to do a rat liver perfusion experiment. As the cellular
structure of the liver is maintained intact in this experiment you can
confidently elucidate the role of liver in the generation of this
metabolite.
I hope this helps.
Incase you require any further clarification, feel free to e-mail me.
Good luck
Ravi
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The following message was posted to: PharmPK
Dear Yang
The isolated perfused rat liver is a powerful model to support PK
studies
and the hepatic metabolism of a molecule, it allows collecting in
dynamics
the bile since the liver is perfused by semi synthetic blood
supplemented by
biliary acids so that hepatic homeostasis is maintained. The bile flow
rate
is stable over 3 hours and is about 1 uL/g/min. With IPRL you can
obtain the
kinetic profile of your metabolite in the bile.
During the perfusion of the liver with the parent drug, you can also
used
phase I or phase II inhibitors in order to observe increase or
decrease of
the metabolite content and thus to better understand enzymatic systems
involved in the metabolism of your compound
Hoping this helps
Francoise BREE
XENOBLIS
Saint Gregoire
France
francoise.bree.aaa.xenoblis.com
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Dear yang
You had been sayed about M+16 metabolite .this metabolite formation is
possibility with Phase -I metabolism . you must and should get the
metabolite in microsomes which gives the Phase-I metabolism and your
not getting even in Hepatocyte which gives the confirmation from Phase-
I & II metabolism.
Now you go for, more confirmation whether that metabolite
fragmentation pattern is truely matching with your parent compound.
i am not give any answer to your question. I hope it may help indirectly
Ravindranath reddy.G
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