Bernier M, Strévey J, Brunette M G, Béliveau R
Biochem Biophys Res Commun. 1984 Sep 17;123(2):562-8. doi: 10.1016/0006-291x(84)90266-3.
Na+ uptake was measured in brush border membrane isolated from rat kidney cortex. In the presence of 100 mM NaCl gradient, Na+ equilibrated across the membranes within 30 minutes, but uptake was linear only for the first 10 seconds. Total uptake could be analysed in terms of a diffusion component and a saturable component (Kt = 5 mM, Jmax = 0.62 pmol/microgram prot/s). Uptake at 1 mM NaCl was found to be inhibited at 60% by amiloride; stimulation of uptake by pH gradient (inside greater than outside) supports the functioning of a Na+-H+ antiport. Uptake at 100 mM NaCl was insensitive to amiloride in the absence of pH gradient. The influence of anions on Na+ uptake was in agreement with known permeabilities for generation of electrical potentials (Thiocyanate greater than chloride greater than gluconate) and was observed at 100 mM Na+ but not at 40 microM. These results suggest that rat renal brush border membrane vesicles are leaky towards Na+ and present a permeability coefficient for Na+ much higher than what is expected from the in vivo conditions.
在从大鼠肾皮质分离的刷状缘膜中测量了Na⁺摄取。在存在100 mM NaCl梯度的情况下，Na⁺在30分钟内跨膜达到平衡，但摄取仅在前10秒呈线性。总摄取可以根据扩散成分和可饱和成分进行分析（Kt = 5 mM，Jmax = 0.62 pmol/微克蛋白/秒）。发现在1 mM NaCl时，氨氯吡脒可抑制60%的摄取；pH梯度（内部大于外部）对摄取的刺激支持Na⁺-H⁺反向转运体的功能。在没有pH梯度的情况下，100 mM NaCl时的摄取对氨氯吡脒不敏感。阴离子对Na⁺摄取的影响与已知的产生电势的通透性一致（硫氰酸盐大于氯离子大于葡萄糖酸盐），并且在100 mM Na⁺时观察到，但在40 μM时未观察到。这些结果表明，大鼠肾刷状缘膜囊泡对Na⁺有渗漏，并且呈现出的Na⁺通透性系数远高于体内条件下预期的值。
