Sodium-dependent lysine flux across bullfrog alveolar epithelium.
Sodium-dependent lysine flux across bullfrog alveolar epithelium.
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穿过牛蛙肺泡上皮的钠依赖性赖氨酸通量。
DOI：
10.1152/jappl.1988.65.4.1655
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发表时间：
1988
期刊：
影响因子：
--
通讯作者：
Crandall,ED
中科院分区：
文献类型：
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作者：
Kim,KJ;Crandall,ED
通过在尤斯室中测量放射性标记的赖氨酸通量穿过牛蛙肺来研究穿过肺泡上皮屏障的氨基酸转运。在不存在透壁电梯度的情况下，将L-[14C]赖氨酸滴注到上游储库中，并测定下游储库中放射性标记的出现率。同时使用同一动物的两个肺来确定流入和流出肺泡浴的示踪剂通量。结果表明，在沐浴液中存在钠的情况下，在肺泡到胸膜方向测量的放射性标记通量大于在相反方向测量的放射性标记通量。 L-[14C]赖氨酸的净通量可被[Na+]饱和，Na+的表观传输系数(Kt)为28mM。 [14C]赖氨酸通量与[Na+]的希尔分析表明钠和放射性标记的L-赖氨酸之间的耦合比为1:1。作为 [L-赖氨酸] 函数的总 L-赖氨酸通量也是饱和的，L-赖氨酸的 Kt 为 7.3 mM。哇巴因显着降低吸收（肺泡到胸膜）放射性标记通量，同时略微增加在相反方向观察到的通量。 L-亮氨酸完全抑制L-[14C]赖氨酸的吸收净通量。另一方面，α-甲基氨基异丁酸(MeAIB)仅略微降低L-[14C]赖氨酸的净通量与对照值的比较。穿过肺泡上皮屏障的净吸收性、Na+依赖性氨基酸通量的存在表明该组织能够通过耦合的共转运机制从肺泡液中去除氨基酸和钠，这对于肺泡上皮的蛋白质代谢和液体平衡可能很重要。
Amino acid transport across the alveolar epithelial barrier was studied by measuring radiolabeled lysine fluxes across bullfrog lungs in an Ussing chamber. In the absence of a transmural electrical gradient, L-[14C]lysine was instilled into the upstream reservoir and the rate of appearance of the radiolabel in the downstream reservoir was determined. Two lungs from the same animal were used simultaneously to determine tracer fluxes both into and out of the alveolar bath. Results showed that the radiolabel flux measured in the alveolar to the pleural direction was greater than that measured in the opposite direction in the presence of sodium in the bathing fluids. The net flux of L-[14C]lysine was saturable with [Na+], with an apparent transport coefficient (Kt) of 28 mM for Na+. Hill analysis of [14C]lysine flux vs. [Na+] indicated a coupling ratio of 1:1 between sodium and radiolabeled L-lysine. Total L-lysine flux as a function of [L-lysine] was also saturable, with Kt of 7.3 mM for L-lysine. Ouabain significantly decreased absorptive (alveolar-to-pleural) radiolabel flux, while slightly increasing the flux observed in the opposite direction. L-leucine completely inhibited absorptive net flux of L-[14C]lysine. alpha-Methylaminoisobutyric acid (MeAIB), on the other hand, only slightly reduced net flux of L-[14C]lysine from the control value. The presence of a net absorptive, Na+-dependent amino acid flux across the alveolar epithelial barrier indicates that the tissue is capable of removing amino acids and sodium from the alveolar fluid by a coupled cotransport mechanism, which may be important for both protein metabolism and fluid balance by alveolar epithelium.