Vari R C, Ott C E
Am J Physiol. 1982 Jun;242(6):F575-9. doi: 10.1152/ajprenal.1982.242.6.F575.
It has been reported that the concentration of chloride in the proximal tubule is greater than that in plasma in several mammalian species. Much of the theory concerning fluid and electrolyte reabsorption in the proximal tubule is based on data taken from in vitro isolated proximal tubules of the rabbit nephron. This study measured in vivo the rabbit proximal tubule fluid-to-ultrafiltrate chloride concentration ratio [(TF/UF)Cl] and its relationship to proximal tubule length as estimated by the tubule fluid-to-plasma inulin concentration ratio [(TF/P)In]. From six rabbits, 19 random proximal tubules were micropunctured and analyzed for inulin and chloride concentrations, the latter being measured by microelectrometric titration. Plasma ultrafiltrate was determined by correcting plasma chloride concentration for protein concentration. The average single nephron filtration rate was 20.2 +/- 0.8 nl/min. The (TF/UF)Cl ratio was 1.10 +/- 0.03, which was significantly different from unity. Furthermore, regression analysis yielded no significant correlation between the (TF/UF(Cl and (TF/P)In ratio. This study demonstrates that a tubule lumen-to-plasma chloride concentration gradient exists in the in vivo proximal tubule of the rabbit that is apparently established early and is not correlated with proximal tubule length.
据报道，在几种哺乳动物中，近端小管中的氯离子浓度高于血浆中的氯离子浓度。许多关于近端小管中液体和电解质重吸收的理论是基于从兔肾单位体外分离的近端小管获得的数据。本研究在体内测量了兔近端小管液与超滤液的氯离子浓度比[（TF/UF）Cl]及其与近端小管长度的关系，近端小管长度通过小管液与血浆菊粉浓度比[（TF/P）In]估算。从6只兔子身上，对19条随机选取的近端小管进行了微穿刺，并分析了菊粉和氯离子浓度，后者通过微电滴定法测量。通过校正血浆中蛋白质浓度来测定血浆超滤液。平均单肾单位滤过率为20.2±0.8 nl/min。（TF/UF）Cl比为1.10±0.03，与1有显著差异。此外，回归分析显示（TF/UF）Cl与（TF/P）In比之间无显著相关性。本研究表明，兔体内近端小管中存在管腔与血浆之间的氯离子浓度梯度，该梯度显然在早期就已建立，且与近端小管长度无关。
