Windus D W, Klahr S, Hammerman M R
Am J Physiol. 1984 Sep;247(3 Pt 2):F403-7. doi: 10.1152/ajprenal.1984.247.3.F403.
It has been shown that acute respiratory acidosis in dogs results in enhanced renal extraction of L-glutamine from plasma and increased ammonia excretion per nephron. To determine whether a component of the enhanced L-glutamine extraction results from increased transport of L-glutamine across the basolateral membrane into the renal proximal tubular cell, we measured Na+ gradient-dependent L-[3H]glutamine transport in proximal tubular basolateral membrane vesicles isolated from kidneys of normal dogs and from kidneys of dogs following 2 h of acute respiratory acidosis. The initial rate of Na+ gradient-dependent L-[3H] glutamine uptake (15 s) was increased significantly in basolateral membrane vesicles from the acidotic compared with normal dogs. Increased uptake could be measured under conditions in which changes in membrane potential resulting from fluxes of solute were minimized. We conclude that an adaptation occurs in the basolateral membrane of the renal proximal tubular cell during acute respiratory acidosis that allows increased transport of L-glutamine across the membrane into the proximal tubular cell. This adaptation may permit increased ammonia production per nephron.
已表明，犬的急性呼吸性酸中毒会导致肾脏从血浆中对L-谷氨酰胺的提取增强，且每个肾单位的氨排泄增加。为了确定增强的L-谷氨酰胺提取的一个组成部分是否源于L-谷氨酰胺跨基底外侧膜向肾近端小管细胞的转运增加，我们测量了从正常犬的肾脏以及急性呼吸性酸中毒2小时后的犬的肾脏中分离出的近端小管基底外侧膜囊泡中Na⁺梯度依赖性L-[³H]谷氨酰胺的转运。与正常犬相比，酸中毒犬的基底外侧膜囊泡中Na⁺梯度依赖性L-[³H]谷氨酰胺摄取的初始速率（15秒）显著增加。在溶质通量引起的膜电位变化最小化的条件下可以测量到摄取增加。我们得出结论，在急性呼吸性酸中毒期间，肾近端小管细胞的基底外侧膜会发生适应性变化，使L-谷氨酰胺跨膜向近端小管细胞的转运增加。这种适应性变化可能使每个肾单位的氨生成增加。
