Characteristics of salt and water transport in superficial and juxtamedullary straight segments of proximal tubules.
Characteristics of salt and water transport in superficial and juxtamedullary straight segments of proximal tubules.
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近端小管浅表和近髓直段盐和水转运的特征。
DOI：
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发表时间：
1975
影响因子：
15.9
通讯作者：
J. P. Kukko
中科院分区：
文献类型：
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作者：
S. Kawamura;M. Imai;D. Seldin;J. P. Kukko
本研究的目的是表征盐和水的运输的性质的浅表（SF）和直段的兔近端小管（JM）检查通过体外微灌注技术。当灌流液由模拟血浆超滤液的溶液组成时，SF和JM直小管之间在液体的净重吸收（SF = 0.47 nl/mm/min; JM = 0.56 nl/mm/min）或经前庭电位差（PD）（SF =-2.1 mV; JM =-1.8 mV）方面没有差异。从灌注液中去除葡萄糖和丙氨酸对任一直段的PD幅度没有影响。哇巴因降低净重吸收率和PD。在灌注液和浴中用环己基氨基磺酸钠（一种假定的不渗透阴离子）等渗置换氯化钠，导致两个节段的管腔负性增加，而用胆碱-CL（非转运阳离子）置换氯化钠，则使PD接近于零。因此，这些研究表明，钠是通过产生PD（产电过程）的主动非偶联过程从近端直小管转运出来的。当灌注液由具有高氯化物浓度的溶液组成时（由于近曲小管中HCO3的重吸收大于Cl的重吸收），SF和JM小管中产生不同的PD：SF =+1.6 ± 0.2 mV; JM =-1.3 ± 0.3 mV。PD的这种差异归因于这两个节段中Na和Cl渗透性的相对差异。电生理学和同位素估计的氯钠渗透性显示，SF小管是约两倍的渗透性，以氯化物比钠，而JM小管是约两倍的渗透性，以钠比氯化物。结果表明，近曲小管直段钠离子主动转运的机制与曲段不同，SF和JM直段钠离子和氯离子的渗透性也不同。
The purpose of the present studies was to characterize the nature of salt and water transport out of the superficial (SF) and juxtamedullary (JM) straight segments of rabbit proximal tubules as examined by in vitro microperfusion techniques. When the perfusate consisted of a solution simulating ultrafiltrate of plasma, there were no differences between SF and JM straight tubules in either net reabsorption of fluid (SF=0.47 nl/mm per min; JM=0.56 nl/mm per min) or in transtubular potential difference (PD) (SF=-2.1 mV; JM=-1.8 mV). Removal of glucose and alanine from the perfusate had no effect on the magnitude of the PD in either straight segment. Ouabain decreased both the net reabsorptive rates and the PD. Isosmolal replacement of NaCL by Na-cyclamate (a presumed impermeant anion) in the perfusate and the bath caused an increase in luminal negativity in both segments wheras similar substitution of NaCL by choline-CL (nontransported cation) changed the PD TO NEAR ZERO. These studies, therefore, suggest that sodium is transported out of the proximal straight tubules by an active noncoupled process that generates a PD (electrogenic process). When the perfusate consisted of a solution with a high chloride concentration (resulting from greater HCO3 than CI reabsorption in the proximal convoluted tubule), different PDs in SF and JM tubules were generated: SF=+1.6 plus or minus 0.2 mV; JM=-1.3 plus or minus 0.3 mV. This difference in PD was attributed to relative differences in Na and CI permeabilities in these two segments. Electrophysiological and isotopic estimates of the chloride to sodium permeability revealed that the SF tubule is about twice as permeant to chloride than to sodium whereas the JM tubules are approximately twice as permeant to sodium than to chloride. It is concluded that the mechanism of active sodium transport in the straight segment of proximal tubule differs from that of the convoluted segment and that both the SF and JM straight segments differ from each other with respect os sodium and chloride permeability.