Effects of dietary fiber on intestinal ion fluxes in rats

The effect of short-term fiber ingestion on jejunal ion fluxes was evaluated in rats using a standard Ussing chamber technique. Ingestion of cellulose and pectin decreased the mucosal to serosal fluxes of both Na and Cl but did not significantly alter serosal to mucosal fluxes; net fluxes of both Na and Cl were significantly lower in the group supplemented with dietary fiber as compared to those animals fed a fiber-free diet. Both potential difference and short-circuit current were higher in the fiber-free group than in the group supplemented with dietary fiber; tissue conductance, however, was unaffected by fiber ingestion. The residual flux of all three groups was virtually identical suggesting that electrical alterations observed after cellulose and pectin ingestion are not the result of ion fluxes other than Na and Cl. These data, coupled with previous observations that short-term fiber supplementation impairs glucose and leucine absorption, suggest that fiber ingestion alters the intestinal membrane, specifically sites of active transport.