Liu F Y, Cogan M G
Am J Physiol. 1984 Nov;247(5 Pt 2):F816-21. doi: 10.1152/ajprenal.1984.247.5.F816.
To measure simultaneously the concentration profiles of bicarbonate, chloride and inulin along the length of the superficial proximal convoluted tubule, free-flow micropuncture measurements were made sequentially from the end-proximal tubule to Bowman's space in 10 tubules of hydropenic Munich-Wistar rats. Bicarbonate and volume reabsorption were 354 +/- 21 pmol X mm-1 X min-1 and 5.9 +/- 0.4 nl X mm-1 X min-1 in the first millimeter and fell progressively in the remaining 3.8 mm of tubule, averaging 83 +/- 4 pmol X mm-1 X min-1 and 2.3 +/- 0.5 nl X mm-1 X min-1, respectively. The values in the initial millimeter represents a high transport capacity since they exceed rates that have been observed when comparable or even higher mean luminal substrate concentrations were presented to the late proximal tubule. In contrast, chloride reabsorption was only 206 +/- 55 peq X mm-1 X min-1 in the first millimeter compared with a mean of 306 +/- 22 peq X mm-1 X min-1 in the rest of the tubule. In conclusion, there is substantial axial transport heterogeneity, with bicarbonate and water reabsorption higher but chloride reabsorption lower in the early compared with the late superficial proximal convoluted tubule.
为了同时测量浅表近端曲管全长上碳酸氢盐、氯离子和菊粉的浓度分布，对10只禁水的慕尼黑-威斯塔大鼠的肾小管进行了自由流微穿刺测量，测量顺序是从近端小管末端到鲍曼囊。在最初的1毫米中，碳酸氢盐和液体重吸收分别为354±21皮摩尔×毫米⁻¹×分钟⁻¹和5.9±0.4纳升×毫米⁻¹×分钟⁻¹，并在肾小管剩余的3.8毫米中逐渐下降，平均分别为83±4皮摩尔×毫米⁻¹×分钟⁻¹和2.3±0.5纳升×毫米⁻¹×分钟⁻¹。最初1毫米处的值代表了较高的转运能力，因为它们超过了向近端小管晚期提供可比甚至更高平均管腔底物浓度时所观察到的速率。相比之下，氯离子重吸收在最初1毫米处仅为206±55皮摩尔×毫米⁻¹×分钟⁻¹，而在肾小管其余部分平均为306±22皮摩尔×毫米⁻¹×分钟⁻¹。总之，存在显著的轴向转运异质性，与浅表近端曲管晚期相比，早期的碳酸氢盐和水重吸收较高，但氯离子重吸收较低。
