Bichara M, Paillard M, Corman B, de Rouffignac C, Leviel F
Am J Physiol. 1984 Jul;247(1 Pt 2):F140-50. doi: 10.1152/ajprenal.1984.247.1.F140.
The effects of extracellular fluid volume expansion on kidney reabsorption of bicarbonate, chloride, and water were examined in Sprague-Dawley rats by paired micropuncture experiments in which tubular fluid was collected from early distal and end-proximal sites. In group I, rats were studied during a plasma-replete euvolemic state and after 10% body wt colloid-free volume expansion. The filtered loads were similar in euvolemia and expansion; expansion increased end-proximal total CO2 concentration ([tCO2] EP) from 13.0 +/- 0.8 to 18.4 +/- 0.7 mM and inhibited the tCO2 fractional reabsorption 26% in the proximal convoluted tubule and 15% in Henle's loop. Early distal tCO2 delivery therefore increased from 61 +/- 7 to 140 +/- 17 pmol X min-1 X g kidney wt-1. A more pronounced inhibition of fractional reabsorption of chloride (45%) and water (35%) occurred in the proximal convoluted tubule during expansion. In group II, rats were studied during 5% body wt 70 g/liter albumin-containing expansion and after 10% body wt colloid-free expansion. Compared with euvolemia of group I, albumin expansion decreased proximal fractional reabsorption of tCO2 13%, chloride 19%, and water 14% without change in filtered loads, and [tCO2]EP rose to 17.2 +/- 0.7 mM. A 10 g/liter decrease in plasma protein concentration during colloid-free expansion was associated, compared with albumin expansion, with inhibition of proximal fractional reabsorption of tCO2 by 4%, chloride by 18%, and water by 9% without further altering [tCO2]EP. We conclude that 1) expansion specifically inhibits bicarbonate reabsorption in the proximal convoluted tubule and in Henle's loop independent of change in filtered load or in peritubular protein concentration, probably by enhancing bicarbonate backdiffusion and reducing proton secretion; 2) expansion-induced decrease in peritubular protein concentration contributes to the proximal expansion effect probably by specifically inhibiting transcellular sodium chloride reabsorption.
通过配对微穿刺实验，从早期远端和近端末端部位收集肾小管液，研究细胞外液量扩张对Sprague-Dawley大鼠肾脏重吸收碳酸氢盐、氯和水的影响。在第一组中，对处于血浆充足的血容量正常状态的大鼠以及体重增加10%的无胶体容量扩张后的大鼠进行研究。血容量正常和容量扩张时的滤过负荷相似；容量扩张使近端末端总二氧化碳浓度（[tCO2]EP）从13.0±0.8 mM升至18.4±0.7 mM，并使近端小管中tCO2的重吸收分数抑制26%，在髓袢中抑制15%。因此，早期远端tCO2输送量从61±7增加至140±17 pmol·min-1·g肾重-1。容量扩张期间，近端小管中氯（45%）和水（35%）的重吸收分数受到更明显的抑制。在第二组中，对体重增加5%的含70 g/L白蛋白的容量扩张期间以及体重增加10%的无胶体容量扩张后的大鼠进行研究。与第一组的血容量正常状态相比，白蛋白容量扩张使近端tCO2、氯和水的重吸收分数分别降低13%、19%和14%，滤过负荷无变化，且[tCO2]EP升至17.2±0.7 mM。与白蛋白容量扩张相比，无胶体容量扩张期间血浆蛋白浓度降低10 g/L与近端tCO2、氯和水的重吸收分数分别抑制4%、18%和9%相关，且未进一步改变[tCO2]EP。我们得出结论：1）容量扩张特异性抑制近端小管和髓袢中的碳酸氢盐重吸收，与滤过负荷或肾小管周围蛋白浓度的变化无关，可能是通过增强碳酸氢盐的反向扩散和减少质子分泌；2）容量扩张引起的肾小管周围蛋白浓度降低可能通过特异性抑制跨细胞氯化钠重吸收而导致近端容量扩张效应。
