Bridges, Janine F (1980) A study of macromolecule absorption in vitro by the small intestine of adult rats. Doctoral thesis, Keele University.

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A method has been developed for the study of macromolecular uptake by the everted sacs of adult rat intestine in vitro. The method incorporated a preparation procedure which minimized temporary hypoxia in the tissue. The complex medium TC 199 containing 10% calf serum and ImM ATP was used as the incubation medium. This medium was shown to have the following advantages over the simple medium traditionally used for the incubation of everted intestinal sacs (i.e. Krebs-Henseleit Ringer).
i) Tissue viability and structural integrity was maintained for longer periods of incubation time (up to 2h).
ii) The absorptive surface was presented with a large variety of substrates therefore macromolecules were not taken up solely because they were the only nutrient available.
A method of calculating results was employed which allowed quantitation of the uptake of different macromolecules, gave an indication of the uptake mechanism and facilitated direct comparison between other cellular systems.
Using the developed method, uptake studies showed that the non- degradable macromolecule [125I]-PVP was taken up into the tissue and accumulated in the serosal fluid linearly with respect to time up to 2h at rates of 0.74 and 0.12 ?l/h/mg protein. Uptake was dependent on substrate concentration, was temperature sensitive and could be inhibited by glycolytic and oxidative phosphorylation inhibitors. This evidence indicated fluid phase pinocytosis to be the mechanism of uptake.
Uptake studies using the degradable macromolecule HRP as substrate showed that the protein was accumulated in the tissue and serosal fluid linearly with time up to 2h at rates of 11.95 and 0.11 ?l/h/mg protein.
HRP was taken up by the tissue about 16 times faster than [125I]-PVP but the rates of accumulation in the serosal space were similar for both macromolecules. This meant that a large proportion (about 99.1%) of the HRP taken up into the tissue was degraded intracellularly.
For both macromolecules, only about 0.07% of the substrate present in the system was transported to the serosal space. The functional significance of these small quantities of macromolecule which are transported across adult intestine is discussed.

Item Type: Thesis (Doctoral)
Subjects: Q Science > QH Natural history > QH301 Biology
Divisions: Faculty of Natural Sciences > School of Life Sciences
Depositing User: Lisa Bailey
Date Deposited: 03 Oct 2019 08:58
Last Modified: 03 Oct 2019 08:58

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