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Hi all,
Caco-2 cell culture is used to study whether a chemical entity is a p-
gp substrate or not. Is it needed that I should confirm the in-vitro
results by p-gp deficient mice?. What are the applications of p-gp
deficient mice?.I have seen some publications where the role of BBB
and renal p-gp transporters studied using p-gp deficient mice.
Whether intestinal p-gp deficient mice are available?.
I will be glad if someone shares the information about intestinal p-gp
deficient mice and their procurement/vendors
Thanks in advance
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Hello,
In my opinion, for extrapolating laboratory results to the clinic, and
also for confirming your in vitro results, it is imperative that you
perform in vivo studies.
A p-gp deficient mouse would
* Help you to understand whether your compound is indeed a
substrate for P-gp or not (if it is not known already)
* Secondly, if your aim is to inhibit the efflux action of P-gp,
and your test compound is a propose P-gp inhibitor, the mouse study
will give you some idea
* Third, to address certain toxicities. P-gp is known to ward off
some of the toxic manifestations. So, a P-gp knock out mouse would
naturally be more sensitive to toxicities. Hence forms an important
leg to your overall study.
As far as vendors are concerned, I presume you might have to use an
mdr1a -/- mouse. Check with Taconic, Inc, they have a huge bank of P-
gp knockout mice!!
Kavita
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The following message was posted to: PharmPK
For one using Caco-2 cells, depending on your experimental setup does
not give good guidance on whether your drug is a P-gp substrate drug
(numerous discussions and differences of opinion etc have passed, like
water under the bridge.........).
So you test in mice and you will have a read out. What is your
reference point, Caco-2 data? So what if you have a flux ratio in
Caco-2 and not any of that is reflected in your mouse experiment. Why
not use MDR1 and Mdr1a expressing renal epithelial cells (LLCPK1 or
MDCKII cells), setup your in vitro experiments and then confirm in the
Mdr1 null mouse model. This way you capture if your drug is as much a
MDR1 as well as a Mdr1a (murine Pgp) substrate drug and chances are
greater that there will be some reasonable correlation between in
vitro data and mouse in vivo outcome
Hope this helps
Regards
Hans
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Dear Chakradhar:
Transporter interaction studies in in vitro models such as the Caco-2
can be relatively inexpensive and useful for a quick check on
substrate status. However, it is not necessary that the transporter
mediated effects will be evident in vivo for a number of reasons
(species differences, compensatory mechanisms and relative extent of
contribution of the particular transporter to the overall
disposition). In vitro studies have to be followed up in vivo to
evaluate the transporter's contribution to ADME in vivo.
I am not sure if P-gp knockouts of specific organs are available. An
alternative would be to use selective P-gp inhibitors to examine their
effect on intestinal absorption. There are two kinds of Pgp-deficient
mice available 1) natural CF1 mutants that lack Pgp (vendor- Charles
river laboratories) and 2) Pgp-knockout mice (Vendor: Taconic Farms).
I would like to emphasize the need for good experimental design and a
thorough literature search for the correct interpretation of
transporter-mediated effects. Recently, we published the effect of P-
gp on the brain penetration of abacavir (Shaik N, DMD 2008). In
addition, the labs of Professor Sugiyama and Dr. Joe Polli have
published numerous publications examining the effect of P-gp in vivo.
Good luck with your studies.
Regards,
Nagdeep
Department of Pharmaceutics
University of Minnesota
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