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Permeability Of Hydrophilic
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| Term Paper Title | Permeability Of Hydrophilic |
| # of Words | 3151 |
| # of Pages (250 words per page double spaced) | 12.6 |
Permeability of Hydrophilic
Permeability of Hydrophilic
Supervisors: Vladan Milovic Professor Per Artursson
SUMMARY
Investigations of the integrity and transport characteristics of 2/4/A1 cells
have been done in this report. The cell line was isolated from rat fetal
intestinal epithelial cells and transfected with thermolabile SV40 large T
antigen.
These cells proliferated at 33 °C, but eliminated the antigen and ceased
proliferating at a non-permissive temperature (39°C). At 39°C 2/4/A1 cells
started to differentiate but simultaneously the cells also underwent massive
cell death.
When cultured at 37°C these cells formed confluent and tight monolayers that
seemed to have paracellular transport characteristics similar to that of the
human intestine. Transmission electron microscopy confirmed the development of
multilayers at 33°C, monolayers at 37°C and defects in the cell layer due to
apoptosis at 39°C.
Different immunostainings of ZO-1, E-cadherin and vinculin confirmed formation
of tight and adherence junctions. Transepithelial resistance reached a plateau
of 25-35 Ohm.cm2, which was similar to the small intestine. In transport studies
2/4/A1 cell line monolayers selectively restricted the permeation of hydrophilic
permeability markers proportional to molecular weight and discriminated more
accurately between the molecules of intermediate molecular weight compared to
Caco-2 cells.
These results indicated that 2/4/A1 cells could be used as a model for
hydrophilic drug absorption.
INTRODUCTION
The small intestine plays a crucial role in the absorption of drugs and
nutrients. Exogenous substances cross a series of barriers during the process
of intestinal absorption: (1) the aqueous boundary/mucus layer, (2) a single
layer of epithelial cells, and (3) the lamina propria, which contains the blood
and lymph vessels that then transport the absorbed drugs to other parts of the
body (Artursson 1991).
The cell monolayer is comprised of two parallel barriers: the cell membrane and
the tight junctions. Most drugs are absorbed by a passive diffusion across the
cell membrane by the transcellular route, or across the tight junctions between
the cells - the paracellular route. Drug transport can also be carrier mediated,
when the drug utilizes transporters located in the cellular membrane.
Transcytosis is another kind of active transport, in which macromolecules can be
transported across the intestinal epithelial cell in endocytosed vesicles.
The hydrophi
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