Tosco M, Orsenigo M N, Gastaldi G, Faelli A
Dipartimento di Fisiologia e Biochimica Generali, Università di Milano, via Celoria 26, I-20133 Milano, Italy.
Am J Physiol Regul Integr Comp Physiol. 2000 May;278(5):R1190-5. doi: 10.1152/ajpregu.2000.278.5.R1190.
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.
我们研究了非洲爪蟾卵母细胞中乳酸转运内源性系统的存在情况。氯离子摄取研究排除了DIDS敏感的阴离子反向转运体作为乳酸移动可能途径的参与。L-[(14)C]乳酸摄取不受叠加pH梯度的影响，在孵育溶液中钠离子存在时受到刺激，并且被单羧酸转运体抑制剂对氯汞苯磺酸盐（pCMBS）严重降低。转运表现出广泛的阳离子特异性，并且被其他单羧酸顺式抑制，主要是被丙酮酸抑制。这些结果表明乳酸摄取主要由一种转运体介导，并且优选的阴离子是丙酮酸。[(14)C]丙酮酸摄取表现出与L-乳酸相同的功能特性模式。计算了两种单羧酸的动力学参数，结果显示对丙酮酸具有更高的亲和力。各种单羧酸转运体抑制剂显著降低了丙酮酸摄取。这些研究表明，非洲爪蟾卵母细胞拥有一个单羧酸转运系统，该系统与哺乳动物单羧酸共转运体家族成员具有一些共同的功能特征，但同时也表现出一些特殊性质，主要涉及阳离子特异性。
