Interaction of bile salts with gastrointestinal mucins |
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Authors: | Email author" target="_blank">Timothy?Scott?WiedmannEmail author Wei?Liang Heather?Herrington |
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Affiliation: | (1) Department of Pharmaceutics, University of Minnesota, 308 Harvard St. SE, 55455 Minneapolis, Minnesota;(2) Present address: Biophysical Institute of Chinese Academy of Science, Beijing, China |
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Abstract: | The properties of three mucins were examined to identify the structural features responsible for their functional differences.
Bovine submaxillary mucin (BSM), porcine gastric mucin (PGM), and rat intestinal mucin (RIM) were each characterized, and
high carbohydrate contents were found for RIM and PGM. The amino acid compositions were typical of mucin glycoproteins, with
over half comprising small, neutral amino acids. Thereafter, each mucin was equilibrated with three different series of concentrations
of the bile salts sodium taurocholate, sodium taurodeoxycholate, and sodium taurochenodeoxycholate. Following multiple centrifugations,
the supernatant and mucin pellet concentrations of the bile salts were measured. The bile salt pellet concentration was plotted
as a function of supernatant concentration, and from the slopes, the excluded volumes were calculated as 25, 29–44, and 28–55
mL/g for BSM, RIM, and PGM, respectively. The intercepts were 8–10, 2–3, and 1–3 mM for BSM, RIM, and PGM, respectively, which
represents an estimate of the bound concentration of bile salt. Differences among the bile salts were observed in the excluded
volume and amount bound, but no trends were evident. The bile salts may interact as aggregates with the hydrophobic areas
and carbohydrate side chains of the mucins, providing favorable sites for association. The binding at low concentrations with
exclusion at high concentrations is significant for modulating the absorption of lipid aggregates from the intestine. Finally,
the differences among the mucins reflect the unique structure-function relationship of these gastrointestinal mucins. |
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