兔肾髓质厚升支中的铵转运：钠、钾、氯共转运体的作用。
Ammonium transport in medullary thick ascending limb of rabbit kidney: involvement of the Na+,K+,Cl(-)-cotransporter.
作者信息
Kinne R, Kinne-Saffran E, Schütz H, Schölermann B
出版信息
J Membr Biol. 1986;94(3):279-84. doi: 10.1007/BF01869723.
In order to investigate the question whether ammonium reabsorption in the thick ascending limb of Henle's loop (TALH) proceeds via the Na+,K+,Cl(-)-cotransporter, plasma membrane vesicles were prepared from TALH cells isolated from rabbit kidney outer medulla and the effect of NH+4 on their transport properties was investigated. It was found that, in the presence of a 78-mmol/liter NaCl gradient, 5 mmol/liter NH+4 inhibited bumetanide-sensitive rubidium flux by 86%; a similar decrease was observed for 5 mmol/liter, K+. Inhibition of bumetanide-sensitive rubidium uptake by NH+4 was competitive and an apparent Ki of 1.9 mmol/liter was found. Bumetanide-sensitive sodium uptake measured in the presence of a 83 mmol/liter KCl gradient was not inhibited by 5 mmol/liter NH+4. A 100-mmol/liter NH4Cl gradient was, however, capable of stimulating bumetanide-sensitive sodium uptake to the same extent as a KCl gradient. These data suggest that NH+4 is accepted by the K+ site of the Na+,K+,Cl-cotransport system and that the transporter can function in a Na+,NH+4,2Cl mode. Since the affinity of the transporter for NH+4 lies in the concentration range found in the TALH lumen in vivo, it is concluded that Na+,NH+4,2Cl-cotransport can contribute to the NH+4 reabsorption in this tubular segment.
为了研究亨氏袢升支粗段（TALH）中的铵重吸收是否通过Na⁺、K⁺、Cl⁻共转运体进行，从兔肾外髓质分离的TALH细胞制备了质膜囊泡，并研究了NH₄⁺对其转运特性的影响。结果发现，在存在78 mmol/L NaCl梯度的情况下，5 mmol/L NH₄⁺使布美他尼敏感的铷通量降低了86%；5 mmol/L K⁺也观察到类似的下降。NH₄⁺对布美他尼敏感的铷摄取的抑制是竞争性的，表观Ki为1.9 mmol/L。在存在83 mmol/L KCl梯度的情况下测量的布美他尼敏感的钠摄取不受5 mmol/L NH₄⁺的抑制。然而，100 mmol/L NH₄Cl梯度能够刺激布美他尼敏感的钠摄取，其程度与KCl梯度相同。这些数据表明，NH₄⁺被Na⁺、K⁺、Cl⁻共转运系统的K⁺位点所接受，并且该转运体可以以Na⁺、NH₄⁺、2Cl⁻模式发挥作用。由于转运体对NH₄⁺的亲和力处于体内TALH管腔中发现的浓度范围内，因此得出结论，Na⁺、NH₄⁺、2Cl⁻共转运可以促进该肾小管节段中的铵重吸收。
Zotero 插件