Transepithelial water and urea permeabilities of isolated perfused Munich-Wistar rat inner medullary thin limbs of Henle's loop.
Transepithelial water and urea permeabilities of isolated perfused Munich-Wistar rat inner medullary thin limbs of Henle's loop.
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离体灌注慕尼黑威斯塔大鼠亨利氏袢内髓细肢的跨上皮水和尿素渗透性。
DOI：
10.1152/ajprenal.00491.2013
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发表时间：
2014
期刊：
影响因子：
--
通讯作者：
Pannabecker,ThomasL
中科院分区：
文献类型：
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作者：
Nawata,CMichele;Evans,KristenK;Dantzler,WilliamH;Pannabecker,ThomasL
为了更好地了解水和尿素通量在尿液浓缩机制中的作用，我们测定了慕尼黑-Wistar大鼠离体长循环下行细肢(DTLS)和升支细肢(ATLS)的跨上皮渗透压水通透性(PF)和尿素通透性(PUREA)。在外髓(上内髓)下方0.5~2.5 mm处或内髓末端2.5 mm处分离出细长肢体。根据水通道水通道蛋白1的结构特征和基因表达水平来表征片段类型，水通道蛋白1在DTL上部高，在DTL下部缺失，在ATLS中缺失，在DTL中缺失，在ATLS中高表达。DTLupperPf较高(3,204.5±450.3μm/S)，而DTLupperPf极低或无渗透Pf(207.8±241.3μm/S)。慕尼黑-Wistar大鼠ATL此前已被证明具有noPf。DTLupperPure为40.0±7.3×10−5 cm/S，以下组(203.8±30.3×10−5 cm/S)、上组(203.8±35.7×10−5 cm/S)、下组(265.1±49.8×10−5 cm/S)明显高于对照组。Phloretin(0.25 mM)不能减少DTLupperPurea，这表明纯净不是由于尿素转运蛋白UT-A2，UT-A2在短环DTL和靠近外髓的一些内髓DTLs的短部分中表达。总而言之，Pureaa在所有没有渗透Pf的片段中都是相似的，但在DTLper中显著较低，DTLper是一种具有高渗透Pf的片段。这些数据与最初提出的被动机制不一致。
To better understand the role that water and urea fluxes play in the urine concentrating mechanism, we determined transepithelial osmotic water permeability (Pf) and urea permeability (Purea) in isolated perfused Munich-Wistar rat long-loop descending thin limbs (DTLs) and ascending thin limbs (ATLs). Thin limbs were isolated either from 0.5 to 2.5 mm below the outer medulla (upper inner medulla) or from the terminal 2.5 mm of the inner medulla. Segment types were characterized on the basis of structural features and gene expression levels of the water channel aquaporin 1, which was high in the upper DTL (DTLupper), absent in the lower DTL (DTLlower), and absent in ATLs, and the Cl-1channel ClCK1, which was absent in DTLs and high in ATLs. DTLupperPfwas high (3,204.5 ± 450.3 μm/s), whereas DTLlowershowed very little or no osmoticPf(207.8 ± 241.3 μm/s). Munich-Wistar rat ATLs have previously been shown to exhibit noPf. DTLupperPureawas 40.0 ± 7.3 × 10−5cm/s and much higher in DTLlower(203.8 ± 30.3 × 10−5cm/s), upper ATL (203.8 ± 35.7 × 10−5cm/s), and lower ATL (265.1 ± 49.8 × 10−5cm/s). Phloretin (0.25 mM) did not reduce DTLupperPurea, suggesting thatPureais not due to urea transporter UT-A2, which is expressed in short-loop DTLs and short portions of some inner medullary DTLs close to the outer medulla. In summary,Pureais similar in all segments having no osmoticPfbut is significantly lower in DTLupper, a segment having high osmoticPf. These data are inconsistent with the passive mechanism as originally proposed.