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Vol. 303, Issue 3, 1095-1101, December 2002
/
) Mouse Intestine
Gut Barrier Group, University of Manchester and Salford Hospitals
Trust, Hope Hospital, Salford, (R.H.S., J.T.-H., N.B.H., G.W.), and
Pharmaceutical Sciences, Pfizer Global Research & Development, Kent,
United Kingdom (M.H.)
Information on the extent to which xenobiotics interact with
P-glycoprotein (PGP) during transit through the intestine is crucial in
determining the influence of PGP on oral drug absorption. We have
recently described a novel use of isolated ileum from PGP-deficient
mdr1a(
/
) mice to resolve PGP- and non-PGP-dependent drug efflux and
provide a definitive measure of intrinsic drug permeability without
recourse to inhibitors (Stephens et al., 2002). The present study uses
this approach to investigate the impact of PGP on intestinal
permeability of paclitaxel and digoxin in different regions of the
mouse intestine (jejunum, ileum, and proximal and distal colon).
Absorption of paclitaxel and digoxin in tissues from wild-type mice was
low and showed little regional variation. In contrast, absorption of
both drugs was markedly higher in mdr1a(
/
) intestine, although the
increase was highly region-dependent, with the ileum and distal colon
showing the greatest effect and much smaller changes in the jejunum and
proximal colon. These effects were accompanied by the abolition of
paclitaxel and digoxin secretion in mdr1a(
/
) mice, suggesting that
regional variations in intestinal permeability are masked by
differential PGP expression, confirmed by immunoblotting studies.
Propranolol permeability, which is not influenced by PGP, showed
similar regional variation in both wild-type and mdr1a(
/
) tissues,
suggesting that differences are at the level of transcellular
permeability. These data suggest that the ileum and the distal colon
are regions of relatively high transcellular permeability for
xenobiotics that are compensated by enhanced expression of PGP.
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