An endogenous monocarboxylate transport in Xenopus laevis oocytes.
We investigated the existence of an endogenous system for lactate transport in Xenopus laevis oocytes. (36)Cl-uptake studies excluded the involvement of a DIDS-sensitive anion antiporter as a possible pathway for lactate movement. L-[(14)C]lactate uptake was unaffected by superimposed pH gradients, stimulated by the presence of Na(+) in the incubating solution, and severely reduced by the monocarboxylate transporter inhibitor p-chloromercuribenzenesulphonate (pCMBS). Transport exhibited a broad cation specificity and was cis inhibited by other monocarboxylates, mostly by pyruvate. These results suggest that lactate uptake is mediated mainly by a transporter and that the preferred anion is pyruvate. [(14)C]pyruvate uptake exhibited the same pattern of functional properties evidenced for L-lactate. Kinetic parameters were calculated for both monocarboxylates, and a higher affinity for pyruvate was revealed. Various inhibitors of monocarboxylate transporters reduced significantly pyruvate uptake. These studies demonstrate that Xenopus laevis oocytes possess a monocarboxylate transport system that shares some functional features with the members of the mammalian monocarboxylate cotransporters family, but, in the meanwhile, exhibits some particular properties, mainly concerning cation specificity.
Tosco
M
M
Dipartimento di Fisiologia e Biochimica Generali, Università di Milano, via Celoria 26, I-20133 Milano, Italy. marisa.tosco@unimi.it
Orsenigo
M N
MN
Gastaldi
G
G
Faelli
A
A
D015056:1-Methyl-3-isobutylxanthine / Q000494:pharmacology; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid / Q000494:pharmacology; D002731:4-Chloromercuribenzenesulfonate / Q000494:pharmacology; D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D002250:Carbon Radioisotopes; D002352:Carrier Proteins / Q000378:metabolism*; D002412:Cations; D002713:Chlorine / Q000378:metabolism; D003373:Coumaric Acids / Q000494:pharmacology; D005260:Female; D006863:Hydrogen-Ion Concentration; D019344:Lactic Acid / Q000378:metabolism*; D009865:Oocytes / Q000378:metabolism*; D019289:Pyruvic Acid / Q000378:metabolism; D011868:Radioisotopes; D012964:Sodium / Q000494:pharmacology; D019789:Tetraethylammonium / Q000494:pharmacology; D014982:Xenopus laevis
D002250:Carbon Radioisotopes; D002352:Carrier Proteins; D002412:Cations; D003373:Coumaric Acids; D011868:Radioisotopes; C007175:alpha-cyano-4-hydroxycinnamate; D019344:Lactic Acid; D002713:Chlorine; D002731:4-Chloromercuribenzenesulfonate; D019789:Tetraethylammonium; D019289:Pyruvic Acid; D012964:Sodium; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; D015056:1-Methyl-3-isobutylxanthine