Transport of SCFA across the large intestinal epithelium of guinea pig
Engelhardt, W.V.; Luciano, L.; Reale, E.; Gros, G.; Rechkemmer, G.
Acta Veterinaria Scandinavica. Supplementum 86: 103-106
1989
ISSN/ISBN: 0065-1699 PMID: 2699771 Document Number: 335860
This brief review concludes that short-chain fatty acids (SCFA) are present in hindgut contents of guineapigs at high concentrations mostly in the dissociated form. At high concentrations absorption in vivo increases linearly with increasing concentration, suggesting passive transport. Comparison of the permeability of the colonic epithelium to acetic, propionic and butyric acid indicates that in the proximal colon up to 50% of SCFA may be absorbed in the dissociated form. In the distal colon absorption seems to occur mostly in the un-ionized form. Paracellular passage of dissociated SCFA does not occur; dissociated SCFA seems to be absorbed by a transcellular pathway. Membrane lipid fluidity and the differences in the surface area of microvilli may partly explain regional differences in absorption rates of SCFA across the caecal, the proximal and the distal colonic epithelium. For non-ionic diffusion SCFA-anions have to be protonated. H+ ions required may be available from bicarbonate gain, in the caecum and in the proximal colon of guineapigs from Na+-H+ exchange and in the distal colon from the K+-H+ pump. Inhibitor studies show that these mechanisms influence propionate/propionic acid fluxes.