Mathisen O, Monclair T, Raeder M, Kiil F
Am J Physiol. 1979 Mar;236(3):F232-9. doi: 10.1152/ajprenal.1979.236.3.F232.
To study the relationship between proximal tubular reabsorption of bicarbonate, sodium, and chloride, the effects of changes in plasma PCO2 were examined in anesthetized dogs. Distal tubular reabsorption was inhibited by ethacrynic acid; plasma bicarbonate concentration was kept constant at 33.4 +/- 0.3 mM; glomerular filtration rate (GFR) was varied over a wide range to examine glomerulotubular balance (constant fractional reabsorption). Hypercapnia (PCO2, 112.0 +/- 2.5 mmHg) increased bicarbonate reabsorption by about 30%, and hypocapnia (PCO2, 19.8 +/- 0.6 mmHg) decreased reabsorption of bicarbonate by more than 50% and altered reabsorption of sodium, chloride, and bicarbonate in the molar ratios 2.7:1.6:1, respectively. During hypercapnia the range of glomerulotubular balance was extended to a GFR 125% of control. During hypocapnia glomerulotubular balance was present only at GFR below 50% of control; reabsorption of bicarbonate sodium, and chloride was constant at GFR exceeding 50% of control. During metabolic acidosis hypercapnia had no significant effect on reabsorption of bicarbonate, sodium, and chloride. These observations support the hypothesis that bicarbonate reabsorption is the main driving force for osmotic reabsorption of water and NaCl in the proximal tubules.
为了研究近端肾小管对碳酸氢盐、钠和氯的重吸收之间的关系，在麻醉犬身上检测了血浆PCO2变化的影响。用依他尼酸抑制远端肾小管重吸收；血浆碳酸氢盐浓度保持恒定在33.4±0.3 mM；肾小球滤过率（GFR）在很宽的范围内变化以检测球管平衡（恒定分数重吸收）。高碳酸血症（PCO2，112.0±2.5 mmHg）使碳酸氢盐重吸收增加约30%，低碳酸血症（PCO2，19.8±0.6 mmHg）使碳酸氢盐重吸收减少超过50%，并使钠、氯和碳酸氢盐的重吸收摩尔比分别改变为2.7:1.6:1。在高碳酸血症期间，球管平衡范围扩展至GFR为对照值的125%。在低碳酸血症期间，仅在GFR低于对照值的50%时存在球管平衡；在GFR超过对照值的50%时，碳酸氢盐、钠和氯的重吸收保持恒定。在代谢性酸中毒期间，高碳酸血症对碳酸氢盐、钠和氯的重吸收无显著影响。这些观察结果支持了以下假说：碳酸氢盐重吸收是近端小管中水和NaCl渗透性重吸收的主要驱动力。
