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首页> 外文期刊>American Journal of Physiology >Developmental changes in rabbit proximal straight tubule paracellular permeability.
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Developmental changes in rabbit proximal straight tubule paracellular permeability.

机译：兔近端直小管旁细胞通透性的发育变化。

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The early proximal tubule preferentially reabsorbs organic solutes and bicarbonate over chloride ions, resulting in a luminal fluid with a higher chloride concentration than that in blood. From this late proximal tubular fluid, one-half of NaCl reabsorption by the adult proximal tubule is active and transcellular and one-half is passive and paracellular. The purpose of the present in vitro microperfusion study was to determine the characteristics of passive chloride transport and permeability properties of the adult and neonatal proximal straight tubules (PST). In tubules perfused with a late proximal tubular fluid, net passive chloride flux was 131.7 +/- 37.7 pmol x mm(-1) x min(-1) in adult tubules and -17.1 +/- 23.3 pmol x mm(-1) x min(-1) in neonatal proximal tubules (P < 0.01). Chloride permeability was 10.94 +/- 5.21 x 10(-5) cm/s in adult proximal tubules and -1.26 +/- 1.84 x 10(-5) cm/s in neonatal proximal tubules (P < 0.05). Thus neonatal PST have a chloride permeability not different from zero and have no net passive chloride transport. Bicarbonate permeability is also less in neonates than adults in this segment (-0.07 +/- 0.03 x 10(-5) vs. 0.93 +/- 0.27 x 10(-5) cm/s, P < 0.01). Neonatal PST have higher sodium-to chloride and bicarbonate-to-chloride permeability ratios than adult PST. However, mannitol and sucrose permeabilities were not different in adult proximal tubules and neonatal PST. Transepithelial resistance was measured using current injection and cable analysis. The resistance was 6.7 +/- 0.7 Omega x cm(2) in adult tubules and 11.3 +/- 1.4 Omega x cm(2) in neonatal PST (P < 0.01). In conclusion, there are significant maturational changes in the characteristics of the PST paracellular pathway affecting transport in this nephron segment.
机译：早期的近端小管优先吸收有机溶质和碳酸氢根，而不是氯离子，从而导致腔内液中的氯离子浓度高于血液中的氯离子浓度。成年的近端肾小管从近端肾小管液体中吸收的NaCl有一半是主动的，并且是跨细胞的，而另一半则是被动的和旁细胞的。本体外微灌注研究的目的是确定成人和新生儿近端直小管（PST）的被动氯化物转运特性和渗透性。在晚期近端肾小管灌注的小管中，成年小管的净被动氯通量为131.7 +/- 37.7 pmol x mm（-1）x min（-1），而-17.1 +/- 23.3 pmol x mm（-1）新生儿近端小管的x min（-1）（P <0.01）。成人近端小管的氯离子渗透率为10.94 +/- 5.21 x 10（-5）cm / s，新生儿近端小管的氯离子渗透率为-1.26 +/- 1.84 x 10（-5）cm / s（P <0.05）。因此，新生儿PST的氯离子渗透率不为零，并且没有净的被动氯离子转运。在这一部分，新生儿的碳酸氢盐渗透率也比成人低（-0.07 +/- 0.03 x 10（-5）vs. 0.93 +/- 0.27 x 10（-5）cm / s，P <0.01）。新生儿PST的钠盐对氯化物和碳酸氢盐对氯化物的渗透率比成人PST高。然而，在成人近端肾小管和新生儿PST中，甘露醇和蔗糖的渗透率没有差异。使用电流注入和电缆分析测量跨上皮电阻。在成人肾小管中，电阻为6.7 +/- 0.7Ωx cm（2），在新生儿PST中为11.3 +/- 1.4Ωx cm（2）（P <0.01）。总之，影响该肾单位节段运输的PST旁细胞途径的特征发生了重大的成熟变化。

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