SCFA and electrolyte absorption in the colon of three rodent species

The effects of nutritional regime on the colonic absorption of electrolytes, water, and short-chain fatty acids (SCFA) were studied in three rodent species (voles, spiny mice, and laboratory mice) differing in their ecological background. The effects of different levels of SCFA, induced by restriction of food intake, on the capacity of the in situ perfused colon to absorb water and electrolytes was studied. In addition, in vitro experiments were carried out to assess the mechanisms related to electrolyte transport in the proximal and distal colon. Water and solutes absorption from the perfused colon in the food restricted voles were significantly lower compared to voles fed ad libitum. No such effect was recorded in the two murid species. In vitro studies, employing Ussing chambers, were conducted to characterize the sodium and chloride transport mechanisms. In the colon of the voles and spiny mice as well as in the distal colon of the laboratory mice, net Na⁺ flux was not significantly different from that of Cl^-, and both were higher than the measured equivalent short circuit current. The results suggest an electroneutral sodium transport mechanism in all three species. A high capacity to adjust the rate of water absorption to the amount of fermentable substance in the intestine was demonstrated only in the vole.