Alteration of gastrointestinal mucin by fiber feeding in rats.

Alterations in gastrointestinal mucin induced by dietary fiber may affect nutrient bioavailability, cytoprotection of the mucosa or other aspects of gastrointestinal function. To allow quantitative study of gastrointestinal mucin, a polyclonal antibody to the mucin of the rat small intestine was produced by injecting rabbits with a high-molecular-weight subfraction (MW 2 x 10(6)) of purified mucin glycoprotein derived from rat intestinal mucin. An enzyme-linked immunosorbent assay was developed and used for the mucin assay. Three groups of male Wistar rats consumed 5% guar gum, 5% citrus fiber or a fiber-free control diet ad libitum for 4 wk. After an overnight fast, luminal and tissue mucin antibody reactivities were determined in the rat stomach, colon and small intestine. In all groups, total (luminal and tissue) mucin reactivity was greater in the small intestine than in the colon or stomach. The group fed 5% citrus fiber had significantly greater mucin reactivity in luminal samples from stomach and intestine than did the fiber-free control group. Fiber-induced increments in gastrointestinal mucin production or availability may be responsible for several reported consequences of fiber feeding, such as more rapid transit times and delayed or impaired nutrient absorption.