Anion antiport mechanism is involved in transport of lactic acid across intestinal epithelial brush-border membrane.
Intestinal epithelial membrane transport of L-lactic acid was characterized using rabbit jejunal brush-border membrane vesicles (BBMVs). The uptake of L-[(14)C]lactic acid by BBMVs showed an overshoot phenomenon in the presence of outward-directed bicarbonate and/or inward-directed proton gradients. Kinetic analysis of L-[(14)C]lactic acid uptake revealed the involvement of two saturable processes in the presence of both proton and bicarbonate gradients. An arginyl residue-modifying agent, phenylglyoxal, inhibited L-[(14)C]lactic acid transport by the proton cotransporter, but not by the anion antiporter. The initial uptakes of L-[(14)C]lactic acid which are driven by bicarbonate ion and proton gradients were inhibited commonly by monocarboxylic acids and selectively by anion exchange inhibitor 4, 4'-diisothiocyanostilbene-2,2'-disulfonic acid and protonophore carbonylcyanide p-trifluoromethoxyphenylhydrazone, respectively. These observations demonstrate that L-lactic acid is transported across the intestinal brush-border membrane by multiple mechanisms, including an anion antiporter and a previously known proton cotransporter.
Tamai
I
I
Department of Pharmacobio-Dynamics, Faculty of Pharmaceutical Sciences, Kanawawa University, 13-1 Takara-machi, Kanazawa 920-0934, Japan.
Ogihara
T
T
Takanaga
H
H
Maeda
H
H
Tsuji
A
A
D000818:Animals; D017920:Antiporters / Q000378:metabolism*; D001639:Bicarbonates; D001692:Biological Transport / Q000187:drug effects; D002021:Buffers; D002256:Carbonic Anhydrases / Q000378:metabolism; D002352:Carrier Proteins / Q000378:metabolism; D027963:Chloride-Bicarbonate Antiporters; D006863:Hydrogen-Ion Concentration; D007408:Intestinal Absorption; D007413:Intestinal Mucosa / Q000378:metabolism*; D007583:Jejunum / Q000378:metabolism*; D019344:Lactic Acid / Q000378:metabolism*; D008297:Male; D026901:Membrane Transport Proteins; D008871:Microvilli / Q000378:metabolism; D011189:Potassium Chloride; D017680:Potassium Compounds; D011522:Protons; D011817:Rabbits; D013431:Sulfates
D017920:Antiporters; D001639:Bicarbonates; D002021:Buffers; D002352:Carrier Proteins; D027963:Chloride-Bicarbonate Antiporters; D026901:Membrane Transport Proteins; D017680:Potassium Compounds; D011522:Protons; D013431:Sulfates; C067802:intestinal peptide-proton cotransporter; C031512:potassium sulfate; D019344:Lactic Acid; D011189:Potassium Chloride; D002256:Carbonic Anhydrases; C026329:potassium bicarbonate