Fulop M, Brazeau P
J Clin Invest. 1970 Dec;49(12):2315-23. doi: 10.1172/JCI106450.
Moderate increases of ureteral back pressure usually cause decreases of glomerular filtration rate and even greater decreases of sodium excretion. It has been assumed previously that increased ureteral back pressure does not enhance renal tubular sodium reabsorption directly and that the decreases of sodium excretion are caused by the decreases of glomerular filtration rate. In the experiments reported here, the effect of increased ureteral back pressure on urinary sodium excretion was studied in dogs in which changes of filtration rate were minimized by infusing saline while ureteral back-pressure was increased. When ureteral back pressure was increased on one side by 10-23 cm of water, the inulin clearance of the experimental kidney decreased by only 3-12% in 21 experiments, did not change significantly (+/-2%) in eight experiments, and increased by 3-8% in seven experiments. The sodium excretion of the experimental kidney decreased in all experiments regardless of whether its inulin clearance increased, decreased, or was unchanged from control values. When the inulin clearance of the experimental kidney increased or remained unchanged during increased ureteral back pressure, its reabsorption of sodium increased more than could be accounted for by the increase of filtered sodium. When the inulin clearance of the experimental kidney decreased during increased ureteral back pressure, its reabsorption of sodium decreased less than could be accounted for by the decrease of filtered sodium.Therefore, the effect of increased ureteral back pressure to decrease urinary sodium excretion is caused in part by increased tubular reabsorption of sodium.
输尿管背压适度升高通常会导致肾小球滤过率降低，钠排泄量降低得更多。此前人们认为，输尿管背压升高不会直接增强肾小管对钠的重吸收，钠排泄量降低是由肾小球滤过率降低所致。在本报告的实验中，研究了输尿管背压升高对犬尿钠排泄的影响，在升高输尿管背压的同时输注生理盐水，使滤过率变化最小。当一侧输尿管背压升高10 - 23厘米水柱时，在21次实验中，实验肾的菊粉清除率仅降低3 - 12%，在8次实验中无显著变化（±2%），在7次实验中升高3 - 8%。无论实验肾的菊粉清除率相对于对照值是升高、降低还是不变，其实验肾的钠排泄量在所有实验中均降低。当输尿管背压升高时实验肾的菊粉清除率升高或保持不变，其对钠的重吸收增加幅度超过滤过钠增加所能解释的范围。当输尿管背压升高时实验肾的菊粉清除率降低，其对钠的重吸收降低幅度小于滤过钠降低所能解释的范围。因此，输尿管背压升高导致尿钠排泄减少的部分原因是肾小管对钠的重吸收增加。
