REGULATION OF PROXIMAL ACIDIFICATION

我提出的研究项目的目的是调查机制 调节近端肾小管酸化的机制。 具体来说，我会 研究1）小管周围pH或碳酸氢盐浓度的影响， 2）NaCl和水的吸收，对HCO 3吸收的影响，通过体内连续 大鼠近端小管的微灌注。 了初步成效 表明近端酸化由两部分组成：1） 跨细胞质子分泌，当 作为管腔碳酸氢盐浓度的函数进行检查，以及2）小的 被动碳酸氢盐泄漏。 肾小管周围pH升高抑制质子 分泌，并降低最大速率。 肾小管周围pH值降低 相反的效果。 在我的项目的第一部分，我建议进一步 研究肾小管周围pH值的影响：1）时间 pH效应的过程（管周pH将随着管周pH的变化而变化） 毛细血管灌注（持续时间分钟），静脉输注（持续时间 小时），和慢性喂养（持续时间天）; 2）是否管周 影响是由于pH值或[HCO-3]; 3）膜插入的作用， 预制转运蛋白; 4）慢性适应的作用，在缺乏 在研究时改变肾小管周围pH值;和5） 调节慢性适应的激素。 在相关研究中，我将 检查糖皮质激素对近端酸化的影响。 在 合作我将检查体内酸碱异常的影响 利用刷状缘在体外测定Na/H反向转运蛋白活性 膜制备 为了初步研究，我发现了一种效果 近端酸化的流量，我将其归因于一种 管腔扩散屏障 在我的项目的第二部分，我将 进一步研究管腔扩散屏障的可能性， 在细胞的管周侧上存在扩散屏障的可能性。 我 将检查NaCl和H2O通量对碳酸氢盐速率的影响 吸收 如果扩散障碍存在并且水穿过它们， 应拖动重碳酸盐并刺激质子分泌速率。 动力学分析将用于区分管腔或管周 对流效应 拟议的研究沿着我以前的结果 将有助于发展动力学和调节的透彻理解 近端酸化

The purpose of my proposed research project is to investigate the mechanism of regulation of proximal tubular acidification. Specifically, I will investigate the effects of 1) peritubular pH or bicarbonate concentration, and 2) NaCl and water absorption, on HCO3 absorption by in vivo continuous microperfusion of the rat proximal tubule. Preliminary results have demonstrated that proximal acidification consists of two components: 1) transcellular proton secretion which demonstrates saturation kinetics when examined as a function of luminal bicarbonate concentration, and 2) a small passive bicarbonate leak. Increases in peritubular pH inhibited proton secretion and decreased the maximal rate. Decreases in peritubular pH had the opposite effect. In the firts part of my project, I propose further investigate the effect of peritubular pH with respect to: 1) the time course of the pH effect (peritubular pH will be changed with peritubular capillary perfusion (duration minutes), intravenous infusions (duration hours), and chronic feeding (duration days); 2) whether the peritubular effect is due to pH or [HCO-3]; 3) the role of membrane insertion of preformed transporters; 4) the role of chronic adaptation in the absence of altered peritubular pH at the time of study; and 5) the possible role of hormones in mediating the chronic adaptation. In related studies I will examine the effect of glucocorticoids on proximal acidification. In collaboration I will examine the effect of in vivo acid-base abnormalities on Na/H antiporter activity assayed in vitro utilizing a brush border membrane preparation. In order preliminary studies, I have found an effect of flow on proximal acidification which I attributed to the presence of a luminal diffusion barrier. In the second part of my project, I will further investigate the possibililty of a luminal diffusion barrier and the possibility of a diffusion barrier on the peritubular side of the cell. I will examine the effect of NaCl and H20 flux on the rate of bicarbonate absorption. If diffusion barriers exist and water moves through them, bicarbonate should be dragged and the rate of proton secretion stimulated. Kinetic analysis will be used to differentiate a luminal or peritubular convection effect. The proposed studies along with my previous results will help develop a thorough understanding of the kinetics and regulation of proximal acidification.