Cultured ruminal epithelial cells express a large-conductance channel permeable to chloride, bicarbonate, and acetate.
The absorption of short-chain fatty acids (SCFA) from the rumen requires efficient mechanisms for both apical uptake and basolateral extrusion. Previous studies suggest that the rumen expresses a basolateral chloride conductance that might be permeable to SCFA. In order to characterize this conductance in more detail, isolated cultured ruminal epithelial cells were studied with the patch-clamp technique, revealing a whole-cell conductance with p(Cl(-)) approximately p(NO(3) (-)) > p(HCO(3) (-)) > p(acetate(-)) > p(gluconate(-)). Currents could be blocked by diisothiocyanato-stilbene-2,2'-disulfonic acid (1 mmol l(-1) > 100 micromol l(-1)), 5-nitro-2-(3-phenylpropyl-amino)benzoic acid (50 micromol l(-1)), niflumic acid (100 micromol l(-1)), and p-chloromercuribenzoate (1 mmol l(-1)). Single-channel conductance was 350 +/- 7 pS for chloride and 142 +/- 7 pS for acetate. Open probability could be fitted with a three-state gating model. We propose a role for this channel in mediating the permeation of chloride, bicarbonate, and acetate across the basolateral membrane of the ruminal epithelium.
Stumpff
Friederike
F
Institut für Veterinär-Physiologie, Freie Universität Berlin, Germany. stumpff@zedat.fu-berlin.de
Martens
Holger
H
Bilk
Sabine
S
Aschenbach
Jörg R
JR
Gäbel
Gotthold
G
D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid / Q000494:pharmacology; D000085:Acetates / Q000378:metabolism*; D000818:Animals; D001639:Bicarbonates / Q000378:metabolism*; D002478:Cells, Cultured; D002712:Chlorides / Q000378:metabolism*; D004847:Epithelial Cells / Q000378:metabolism; D005232:Fatty Acids, Volatile / Q000378:metabolism; D005942:Gluconates / Q000378:metabolism; D015640:Ion Channel Gating / Q000187:drug effects*; D009566:Nitrates / Q000378:metabolism; D009579:Nitrobenzoates / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D011188:Potassium / Q000378:metabolism; D012417:Rumen / Q000166:cytology / Q000378:metabolism*; D012756:Sheep; D012964:Sodium / Q000378:metabolism; D020245:p-Chloromercuribenzoic Acid / Q000494:pharmacology
D000085:Acetates; D001639:Bicarbonates; D002712:Chlorides; D005232:Fatty Acids, Volatile; D005942:Gluconates; D009566:Nitrates; D009579:Nitrobenzoates; C058176:5-nitro-2-(3-phenylpropylamino)benzoic acid; D020245:p-Chloromercuribenzoic Acid; D012964:Sodium; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; C030691:gluconic acid; D011188:Potassium