title: Absorption of short-chain fatty acids across ruminal epithelium of sheep.
abstract: Investigations on the absorption of shortchain fatty acids across ruminal epithelium of sheep were performed both in vitro (Ussing chamber technique, using propionic acid representatively for short-chain fatty acids) and in vivo (washed, isolated reticulorumen). A pH-induced, nearly tenfold increase in the concentration of undissociated propionate led to an only twofold increase in mucosal-to-serosal flux of propionate (in vitro). Neither amiloride (1 mmol.l-1, in vitro) nor theophylline (10 mmol.l-1, in vivo), inhibitors of the ruminal Na+/H+ exchanger, exerted any significant influence on propionate fluxes or short-chain fatty acids absorption, respectively. Total replacement of luminal Na+ (by choline) did not alter short-chain fatty acids absorption (in vivo). Mucosal 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid (0.1 mmol.l-1) or mucosal nitrate (40 mmol.l-1) markedly reduced propionate net flux (in vitro). Increasing mucosal Cl- concentration brought about a significant drop in mucosal-to-serosal flux of propionate (in vitro) and in short-chain fatty acids net absorption (in vivo), respectively. The results obtained suggest that short-chain fatty acids are absorbed both as anions and as undissociated acids across ruminal epithelium of sheep. It is concluded that short-chain fatty acids anions either compete with Cl- for binding sites at a common anion-exchange mechanism or that they are absorbed by an short-chain fatty acids anion/ HCO3- exchanger indirectly coupled to a Cl-/HCO3- exchanger via intracellular bicarbonate.
authors.affiliation: University of Leipzig, Department of Veterinary Biochemistry, Germany.
authors.forename: T
authors.initials: T
authors.lastname: Kramer
authors.forename: T
authors.initials: T
authors.lastname: Michelberger
authors.forename: H
authors.initials: H
authors.lastname: Gürtler
authors.forename: G
authors.initials: G
authors.lastname: Gäbel
mesh_terms: D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid / Q000494:pharmacology; D000584:Amiloride / Q000494:pharmacology; D000818:Animals; D001693:Biological Transport, Active / Q000187:drug effects; D002712:Chlorides / Q000378:metabolism / Q000494:pharmacology; D004848:Epithelium / Q000187:drug effects / Q000378:metabolism; D005232:Fatty Acids, Volatile / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D007408:Intestinal Absorption / Q000187:drug effects; D009566:Nitrates / Q000494:pharmacology; D011422:Propionates / Q000378:metabolism; D012417:Rumen / Q000187:drug effects / Q000378:metabolism*; D012756:Sheep / Q000378:metabolism*; D012964:Sodium / Q000378:metabolism / Q000494:pharmacology; D017923:Sodium-Hydrogen Exchangers / Q000378:metabolism; D013806:Theophylline / Q000494:pharmacology
chemical_list: D002712:Chlorides; D005232:Fatty Acids, Volatile; D009566:Nitrates; D011422:Propionates; D017923:Sodium-Hydrogen Exchangers; D000584:Amiloride; D012964:Sodium; D013806:Theophylline; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid