Mechanisms of ion transport across the loop of Henle : Regulation by hormones and drugs

众所周知，粗大的Henle‘s lop(TAL)升支由两种不同类型的细胞组成，表面光滑(S细胞)或表面粗糙(R细胞)。该项目旨在阐明这种细胞异质性的功能意义。为此，我们进行了组织计量学分析、电生理研究和离子通量测量。TAL沿肾轴线的组织计量学分析表明，R细胞在皮质部分(皮质厚升肢)较多，而S细胞在髓质部(髓质厚升肢)较多。随机细胞穿刺法显示，有两类细胞具有不同的基侧K电导：高基侧电导细胞(HBC)和低基侧电导细胞(LBC)。结合K流研究，我们提出了S细胞^=HBc细胞^=K吸收细胞，R细胞^=LBC细胞^=K分泌细胞的方案。大鼠去肾上腺后，HBC细胞基侧膜电导有降低的趋势。糖皮质激素(地塞米松)的替代治疗改善了这种异常，而盐皮质激素(醛固酮)的替代治疗没有任何效果。去肾上腺动物的MAL钾吸收减少，经地塞米松治疗后恢复，但不能通过注射醛固酮恢复。在这些观察的基础上，我们得出结论，糖皮质激素作用于R细胞，增加了基底外侧膜的钾电导，从而增加了该节段的钾吸收。沿粗大升支的形态异质性可能对钾在肾脏中的转运具有功能意义。

It is well known that the thick ascending limb of Henle's lop (TAL) consists of two distinct types of cells having smooth surface (S cell) or rough surface (R cell). This project was designed to clarify the functional significance of this cell heterogeneity. For this purpose, we made histometrical analyzes, electrophysiological studies and ion flux measurements. The histometrical analysis of the TAL along the renal axis revealed that R-cells are abundant in the cortical portion (cortical thick ascending limb, CAL), whereas S-cells are rich in the medullary portion (medullary thick ascending limb, MAL). Random cell puncture showed that there are two cell populations having different basolateral K conductance ; the high basolateral conductance cell (HBC) and the low basolateral conductance cell (LBC). In combination with K flux studies, we proposed the following schema : S cell^=HBC cell^=K absorptive cell ; and R cell^=LBC cell^=K secretory cell. After andrenalectomy, the basolateral membrane conductance of HBC cells of rat MAL tended to reduce. Replacement of glucocorticoid (dexamethasone) improved this abnormality, whereas that of mineralocorticoid (aldosterone) was without any effects. K absorption was reduced in the MAL obtained from adrenalectomized animals, and recovered by administration of dexamethasone, but not by administratin of aldosterone. Based on these observations, we concluded that glucocorticoids act on R cell to increase the basolateral mambrane K conductance, and thereby increase K absorption across this segment. It is possible that morphological heterogeneity along the thick ascending limb has functional significance with respect to K transport in the kidney.