Absorption of volatile fatty acid, Na, and H2O by the colon of the dog.

Volatile fatty acid (VFA) concentrations were examined in the gastrointestinal tract of dogs 24 and 48 hours after a meal. Small concentrations of VFA were present in the stomach and small intestine. Large concentrations were present in the large intestine at both periods after the meal, but the total quantity was reduced markedly between 24 and 48 hours. Colonic absorption and transport of VFA also were examined with in vitro and in vivo perfusion procedures. Both demonstrate that VFA were rapidly absorbed and that the rate of absorption/cm2 of colonic mucosa ws equivalent to that measured in the pig. In vivo results showed that VFA and Na were absorbed at the same rate, and their absorption showed a parallel increase with a decrease in pH of the perfusate. Absorption of Na and VFA alone could account for osmotic absorption of H2O from the colon. Results indicated that although the total quantity of VFA absorbed by the colon of the dog would be nutritionally insignificant, their absorption is of major importance to normal colonic absorptive processes.