RENAL TUBULAR PCO2 AND ACID-BASE EQUILIBRIUM

本研究采用微电极和微穿刺技术， 在大鼠肾脏中的技术，以评估2个目前的假设， 在近端管腔中产生的CO2的过程中， 重吸收 在第一个假设中， 管腔在细胞中被消耗以产生新的碳酸氢盐; 第二个假设，二氧化碳穿过细胞，直接增加 肾小管周毛细血管PCO 2。 我们计划评估这些假设， 在大鼠肾脏中检测到的两个二氧化碳压力梯度： 1)小的跨上皮梯度，和2）大的毛细血管-动脉 梯度离心 在拟议的实验中，我们将测量管状和 毛细血管PCO 2，近端肾小管重吸收，肾血 流量和肾耗氧量。 测量后两个参数 因为代谢产生的二氧化碳和血液流动可能会影响 二氧化碳分压 这两个假设的预测的计算机模型已经被 开发，以帮助在实验的设计，以区分 假设 将进行自由流动显微穿刺研究， 在碳酸氢盐 重吸收、动脉PCO 2、肾血流量和血细胞比容发生改变。 单个肾单位节段和肾小管周围的原位微灌注 还将进行毛细管测试以评估PCO 2梯度。 我们的实验结果和计算机模型之间的相互作用应该 让我们区分这两个假设，并制定一个 碳酸氢盐重吸收过程的更完整模型 完成了

The proposed research is designed to use microelectrode and micropuncture techniques in the rat kidney to evaluate 2 current hypotheses regarding the fate on the CO2 produced in the proximal tubular lumen in the process of bicarbonate reabsorption. In the first hypothesis, the CO2 produced in the lumen is consumed in the cell in the generation of new bicarbonate; in the second hypothesis, the CO2 crosses the cell and directly increases peritubular capillary PCO2. We plan to evaluate these hypothesis in terms of two CO2 pressure gradients that have been detected in the rat kidney: 1) a small transepithelial gradient, and 2) a large capillary-arterial gradient. In the proposed experiments, we will measure tubular and capillary PCO2, proximal tubular bicarbonate reabsorption, renal blood flow, and renal oxygen consumption. The latter two parameters are measured because metabolic CO2 production and blood flow can potentially influence PCO2. Computer models of the predictions of the 2 hypotheses have been developed to help in the design of experiments to differentiate between the hypotheses. Free-flow micropuncture studies will be carried out to evaluate these PCO2 gradients under conditions in which bicarbonate reabsorption, arterial PCO2, renal blood flow and hematocrit are altered. In situ microperfusion of individual nephron segments and peritubular capillaries will also be carried out to evaluate the PCO2 gradients. Interaction between our experimental results and the computer models should allow us to differentiate between these two hypotheses, and to develop a more complete model of the process by which bicarbonate reabsorption is accomplished.