FACILITATED TRANSPORT OF LACTATE BY RABBIT CORNEAL ENDOTHELIUM
FACILITATED TRANSPORT OF LACTATE BY RABBIT CORNEAL ENDOTHELIUM
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DOI：
10.1006/exer.1994.1082
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发表时间：
1994-07-01
影响因子：
3.4
通讯作者：
BONANNO, JA
中科院分区：
文献类型：
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作者：
GIASSON, C;BONANNO, JA
用pH敏感的细胞内荧光探针研究了质子偶联乳酸跨兔角膜内皮的转运。乳酸转运是载体介导的，并在顶端内皮与H+偶联的功能性指征结果表明：（1）质子内流是乳酸浓度的饱和函数;（2）L-乳酸产生的最大H+内流速度快，与转运体的亲和力高（V-max = 1.6 mM min（-1），表观K-1/2 = 31 mM）高于其光学异构体D-乳酸盐（V-max = 0.9 mM min（-1），表观K-1/2 = 59 mM）;（3）乳酸盐诱导的酸化可被顶端汞水杨酸重复。这些结果与顶端lac（-）：H+协同转运蛋白的存在一致。在去上皮化角膜的基底侧添加乳酸盐时，内皮细胞短暂酸化0.05单位，但随后碱化0.07，0.02单位超过基线。基底外侧乳酸盐诱导的酸化抑制75%的汞水杨酸，而在控制条件下观察到的净碱化不受影响。碱化是Na+依赖性的，但阿米洛利不敏感。碱性化的基础上，乳酸也可以抑制顶端mersalyl。这些结果表明，酸化代表乳酸流入通过基底外侧Lac（-）：H+共转运，而净碱化是由于基底外侧Na+依赖的乳酸摄取和乳酸流出通过顶端Lac（-）：H+共转运。这些促进的运输机制可以提供从高度糖酵解的角膜中有效去除乳酸盐。
Proton coupled lactate transport across the rabbit corneal endothelium was studied using a pH-sensitive intracellular fluorescent probe. Functional indications that lactate transport is carrier-mediated and coupled to H+ at the apical endothelium (aqueous humor facing) that were found were: (1) proton influx was a saturable function of lactate concentration; (2) L-lactate produced a faster maximal H+ influx and had a higher affinity for the transporter (V-max = 1.6 mM min(-1), apparent K-1/2 = 31 mM) than its optical isomer, D-Lactate (V-max = 0.9 mM min(-1), apparent K-1/2 = 59 mM); (3) the lactate-induced acidification was inhibitable by apical mersalyl acid. These results are consistent with the presence of an apical lac(-):H+ cotransporter. On basolateral addition of lactate to a de-epithelialized cornea, the endothelial cells transiently acidified by 0.05 units, but then alkalinized by 0.07, 0.02 units over baseline. The basolateral lactate-induced acidification was inhibited by 75% by mersalyl acid, while the net alkalinization observed under control conditions was unaffected. The alkalinization was Na+-dependent yet amiloride-insensitive. Alkalinization on addition of basolateral lactate could also be inhibited by apical mersalyl. These results suggest that the acidification represents lactate influx through basolateral Lac(-):H+ cotransport while the net alkalinization is due to basolateral Na+-dependent lactate uptake and lactate efflux through apical Lac(-):H+ cotransport. These facilitated transport mechanisms could provide for the efficient removal of lactate from the highly glycolytic cornea.