Osmosis in Cortical Collecting Tubules
Osmosis in Cortical Collecting Tubules
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皮质集合管中的渗透
DOI：
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发表时间：
1974
期刊：
影响因子：
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通讯作者：
T. Andreoli
中科院分区：
文献类型：
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作者：
J. Schafer;S. L. Troutman;T. Andreoli
本实验旨在评价不同渗透压对兔离体皮层集合管抗利尿激素(ADH)非依赖性水和溶质通透性的影响。无肾上腺皮质激素时的渗透水渗透系数(cm S~(-1))Pfl→b(扫描电子显微镜)为20±4×10~(-4)，无ADH时→L为88±15×10~(-4)cm S~(-1)。我们还测定了~(14)C-尿素的表观尿素渗透系数(cm S~(-1))。对低渗腔内液和等渗浴液，P-DD尿素L→b为0.045±0.004×10~(-4)，不受ADH的影响。等渗浴液组L→b和→L组的ADH非依赖性数值分别为0.216±0.022×10~(-4)cm S~(-1)和0.033±0.002×10~(-4)cm S~(-1)。值得注意的是，当蔗糖引起管腔高张时，P-DDUA L→b不升高；洗浴液高张不改变肾小管对水或尿素的通透性。我们对这些数据的解读表明，管腔高张力增加了紧密连接对水和尿素的泄漏，但不会增加蔗糖的泄漏。当紧密连接对尿素开放时，无ADH时Pfb→L的值约为有ADH时Pfl→b值的一半，因此，我们得出结论：紧密连接是腔到浴渗透的一种可以忽略的细胞旁分流。这些发现与前一篇论文中的发现一起，根据水渗透的溶解-扩散模型进行了讨论，在该模型中，ADH增加了管腔质膜中的水的溶解度。
The present experiments were designed to evaluate the effects of varying the osmolality of luminal solutions on the antidiuretic hormone (ADH)-independent water and solute permeability properties of isolated rabbit cortical collecting tubules. In the absence of ADH, the osmotic water permeability coefficient (cm s–1) Pfl→b, computed from volume flows from hypotonic lumen to isotonic bath, was 20 ± 4 x 10–4 (SEM); the value of Pfb→l in the absence of ADH, computed from volume flows from isotonic bath to hypertonic lumen, was 88 ± 15 x 10–4 cm s–1. We also measured apparent urea permeability coefficients (cm s–1) from 14C-urea fluxes from lumen to bath (P DDurea l→b) and from bath to lumen (P DDurea b→l). For hypotonic luminal solutions and isotonic bathing solutions, P DDurea l→b was 0.045 ± 0.004 x 10–4 and was unaffected by ADH. The ADH-independent values of P DDurea l→b and P urea b→l were, respectively, 0.216 ± 0.022 x 10–4 cm s–1 and 0.033 ± 0.002 x 10–4 cm s–1 for isotonic bathing solutions and luminal solutions made hypertonic with urea, i.e., there was an absolute increase in urea permeability and asymmetry of urea fluxes. Significantly, P DDurea l→b did not rise when luminal hypertonicity was produced by sucrose; and, bathing fluid hypertonicity did not alter tubular permeability to water or to urea. We interpret these data to indicate that luminal hypertonicity increased the leakiness of tight junctions to water and urea but not sucrose. Since the value of Pfb→l in the absence of ADH, when tight junctions were open to urea, was approximately half of the value of Pfl→b in the presence of ADH, when tight junctions were closed to urea, we conclude that tight junctions are negligible paracellular shunts for lumen to bath osmosis with ADH. These findings, together with those in the preceding paper, are discussed in terms of a solubility-diffusion model for water permeation in which ADH increases water solubility in luminal plasma membranes.