Capasso G, Evangelista C, Zacchia M, Trepiccione F, Acone D, Cantone A, Pollastro R M, Rizzo M
Chair of Nephrology, School of Medicine, Second University of Naples, Naples, Italy.
J Nephrol. 2006 Mar-Apr;19 Suppl 9:S11-7.
The loop of Henle (LOH) is an important site of renal acidification. Using the in vivo microperfusion technique of LOH combined with quantitative polymerase chain reaction (PCR) performed on isolated thick ascending limbs (TAL), we demonstrated that the Na + -H + exchanger is the main transport mechanism involved, although a small, but significant contribution from the H+-ATPase also occurs. Among the various Na+-H+ exchanger isoforms we have evidenced that NHE3 is expressed and functionally active along the TAL. Since the LOH is exposed to osmotic stress, bicarbonate transport was also measured under medullary hypotonicity conditions, which led to the stimulation of bicarbonate reabsorption. We demonstrated that the LOH can participate in the tubular adaptation to an increased filtered bicarbonate load by increasing net LOH bicarbonate transport. In this setting, at the molecular level, mRNA and protein abundance of NHE3 were also stimulated, and coincided with an increase in NHE3 activity. Finally, NHE3 expression and abundance was highly stimulated in the early phase of diabetes, which is characterized by increased glomerular filtration rate (GFR).
亨氏袢（LOH）是肾脏酸化的重要部位。运用亨氏袢的体内微灌注技术，并结合对分离的髓袢升支粗段（TAL）进行的定量聚合酶链反应（PCR），我们证明了Na⁺-H⁺交换体是主要的转运机制，不过H⁺-ATP酶也有少量但显著的作用。在各种Na⁺-H⁺交换体亚型中，我们已证实NHE3沿髓袢升支粗段表达且具有功能活性。由于亨氏袢会受到渗透应激，因此还在髓质低渗条件下测量了碳酸氢盐转运，结果发现这会刺激碳酸氢盐重吸收。我们证明，亨氏袢可通过增加亨氏袢净碳酸氢盐转运来参与肾小管对滤过碳酸氢盐负荷增加的适应性调节。在此情况下，在分子水平上，NHE3的mRNA和蛋白丰度也受到刺激，且与NHE3活性增加相一致。最后，在以肾小球滤过率（GFR）增加为特征的糖尿病早期，NHE3的表达和丰度受到高度刺激。
