Capasso G, Mollica F, Saviano C, De Santo N G
Chair of Nephrology, School of Medicine, 2nd University of Naples, Italy.
Semin Nephrol. 1995 Sep;15(5):419-25.
An increase in glomerular filtration rate (GFR) induces adaptive changes in tubular function to prevent the urinary loss of water and electrolytes. This is also true for acid-base balance: the increase in filtered bicarbonate load will stimulate H+ secretion at the level of several segments including the proximal tubule, the loop of Henle, and the distal tubule. There is an activation of both the luminal Na+/H+ exchanger and H(+)-ATPase, and basal-lateral Na(+)-HCO3- cotransport which allows an increase in luminal H+ secretion and basal lateral HCO3- exit. The stimulation of electrolyte reabsorption is very important at the level of the thick ascending limb of Henle, a segment that shows consistent hypertrophy in many models of hyperfiltration. Along this segment, increased Na+ and Cl- reabsorption has been found in rats receiving a high-protein diet. The ensuing reduced Na+ and Cl- concentrations, at the level of the macula densa, could weaken the signal responsible for initiating the tubuloglomerular feedback (TGF), thus allowing GFR to increase.
肾小球滤过率（GFR）的增加会引起肾小管功能的适应性变化，以防止水和电解质的尿流失。酸碱平衡也是如此：滤过的碳酸氢盐负荷增加会刺激包括近端小管、髓袢和远端小管在内的多个节段分泌H⁺。管腔Na⁺/H⁺交换体和H⁺-ATP酶以及基底外侧Na⁺-HCO₃⁻共转运体均被激活，从而使管腔H⁺分泌增加，基底外侧HCO₃⁻排出增加。在髓袢升支粗段，电解质重吸收的刺激非常重要，在许多超滤模型中，该节段均表现出持续性肥大。在接受高蛋白饮食的大鼠中，沿该节段发现Na⁺和Cl⁻重吸收增加。随后，致密斑处Na⁺和Cl⁻浓度降低，可能会减弱启动管球反馈（TGF）的信号，从而使GFR增加。
