Functional role of bicarbonate in propionate transport across guinea-pig isolated caecum and proximal colon.
1. Unidirectional fluxes of propionate across isolated epithelia from the guinea-pig caecum and proximal colon were measured under short-circuit current conditions. In the caecum and proximal colon the serosal-to-mucosal propionate flux (JPrsm) was higher than mucosal-to-serosal flux (JPrms), resulting in a net secretory flux of propionate. 2. HCO3(-)-CO2-free solution reduced JPrms in the caecum and proximal colon markedly; JPrsm was not (caecum) or little (proximal colon) affected. The subsequent addition of acetazolamide caused a further decrease in JPrms in the proximal colon, but not in the caecum. 3. In HCO3(-)-containing solutions acetazolamide or ethoxzolamide inhibited JPrms; JPrsm was not affected. A macromolecular carbonic anhydrase inhibitor, prontosil-dextran, had no effect on propionate fluxes, indicating that the intracellular carbonic anhydrase is of importance for short-chain fatty acid transport. 4. Subsequent to carbonic anhydrase inhibition, mucosal addition of amiloride caused a slight further decrease of JPrms in the caecum and proximal colon; JPrsm was not affected. 5. Results support the view that a considerable proportion of short-chain fatty acids (SCFAs) is absorbed via a SCFA(-)-HCO3- exchange.
von Engelhardt
W
W
Department of Physiology, School of Veterinary Medicine, Hannover, Germany.
Gros
G
G
Burmester
M
M
Hansen
K
K
Becker
G
G
Rechkemmer
G
G
D000086:Acetazolamide / Q000494:pharmacology; D000818:Animals; D001639:Bicarbonates / Q000378:metabolism*; D002256:Carbonic Anhydrases / Q000378:metabolism; D002432:Cecum / Q000187:drug effects / Q000378:metabolism*; D003106:Colon / Q000187:drug effects / Q000378:metabolism*; D003911:Dextrans / Q000494:pharmacology; D005016:Ethoxzolamide / Q000494:pharmacology; D006168:Guinea Pigs; D007413:Intestinal Mucosa / Q000187:drug effects / Q000378:metabolism*; D017136:Ion Transport / Q000187:drug effects; D008297:Male; D011422:Propionates / Q000378:metabolism*; D010128:p-Aminoazobenzene / Q000031:analogs & derivatives / Q000494:pharmacology; D044482:Benzeneacetamides
D000086:Acetazolamide; D001639:Bicarbonates; D002256:Carbonic Anhydrases; D003911:Dextrans; D005016:Ethoxzolamide; D011422:Propionates; D010128:p-Aminoazobenzene; C003359:sulfamidochrysoidine; D044482:Benzeneacetamides