An in vitro study of short-chain fatty acid concentrations, production and absorption in pig (Sus scrofa) colon.

1. Short-chain fatty acid concentration was 180 mmol/l in the proximal colon and decreased to 108 mmol/l in the rectum. 2. Fermentation in chymus from different regions of the colon, showed the pattern of end products to reflect the substrate and not the site of the colon. 3. Isolated mucosa from proximal and distal colon had electroneutral sodium absorption of 4.8 +/- 0.2 and 2.9 +/- 0.8 mueq/cm2 hr in bicarbonate free media, which was abolished in the absence of chloride. 4. Electroneutral sodium absorption was enhanced by short-chain fatty acids in the proximal colon and could be described by Michaelis-Menten kinetics with Km 2.0-11 mmol/l and Jm 1.6-3.6 mueq/cm2 hr. In the distal colon the stimulation was smaller and propionate even inhibited sodium absorption. 5. Butyrate was absorbed in the proximal colon, whereas acetate and propionate, and butyrate in the distal colon had a flux ratio of one. 6. Amiloride (5 mmol/l) inhibited sodium absorption and net butyrate absorption.