Acid extrusion in S3 segment of rabbit proximal tubule. II. Effect of basolateral CO2/HCO3-.
Acid extrusion in S3 segment of rabbit proximal tubule. II. Effect of basolateral CO2/HCO3-.
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兔近曲小管 S3 段酸挤出。
DOI：
10.1152/ajprenal.1995.268.2.f193
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发表时间：
1995
期刊：
影响因子：
--
通讯作者：
Boron,WF
中科院分区：
文献类型：
--
作者：
Chen,LK;Boron,WF
监测细胞内的pH敏感染料二甲基羧基荧光素的吸收光谱，我们研究了细胞内的pH值（pHi）的调节在离体灌注的兔近端小管S3段。在前一项研究中，J.Physiol.268（肾液电解质生理学37）：F179-F192，1995.]，我们证明了同时向管腔和浴中加入CO2/HCO 3-刺激了两种酸挤出机制，一种依赖于管腔Na+（Na+/H+交换器），另一种不依赖于Na+（可能是H+泵）。在这里，我们研究了仅向内腔或仅向浴中添加CO2/HCO 3-的影响。在一个广泛的pHi范围内，总速率的pHi恢复从酸负荷在Na+的存在下，没有增加管腔CO2/HCO 3-。另一方面，基底侧CO2/HCO 3-增加pHi恢复率的程度甚至大于双侧CO2/HCO 3-。关于Na（+）-非依赖性pHi恢复机制，我们发现与在不存在Na+的情况下研究的对照相比，鲁米那CO2/HCO 3-未能增加pHi恢复速率。管腔CO2/HCO 3-也没有显著影响最大酸负荷和Na（+）非依赖性pHi恢复开始之间的滞后时间（约147秒，对照组约212秒）。另一方面，仅向浴中添加CO2/HCO 3-显著增加了Na（+）-非依赖性pHi恢复的速率，其通常大于用双侧CO2/HCO 3-观察到的速率。在浴中仅CO2/HCO 3-也将滞后时间减少到约51 s，这与双侧CO2/HCO 3-观察到的约36 s的值没有显著差异。我们的数据是一致的假设，基底外侧（但不是管腔）CO2/HCO 3-刺激管腔Na+/H+交换和管腔H+泵。
Monitoring intracellular absorbance spectra of the pH-sensitive dye dimethylcarboxyfluorescein we studied intracellular pH (pHi) regulation in the isolated perfused S3 segment of the rabbit proximal tubule. In the preceding study [Am. J. Physiol. 268 (Renal Fluid Electrolyte Physiol. 37): F179-F192, 1995.], we demonstrated that simultaneously adding CO2/HCO3- to both lumen and bath stimulated two acid-extruding mechanisms, one dependent on luminal Na+ (a Na+/H+ exchanger) and one independent of Na+ (presumably a H+ pump). Here, we examine the effects of adding CO2/HCO3- to the lumen only or to the bath only. Over a broad pHi range, the total rate of pHi recovery from an acid load in the presence of Na+ was not increased by luminal CO2/HCO3-. On the other hand, basolateral CO2/HCO3- increased the pHi recovery rate to an even greater extent than had bilateral CO2/HCO3-. Regarding the Na(+)-independent pHi recovery mechanism, we found that luminal CO2/HCO3- failed to increase the pHi recovery rate compared with controls also studied in the absence of Na+. Neither did luminal CO2/HCO3- significantly affect the lag time between the maximal acid load and the initiation of the Na(+)-independent pHi recovery (approximately 147 vs. approximately 212 s in controls). On the other hand, adding CO2/HCO3- to only the bath substantially increased the rate of Na(+)-independent pHi recovery, which generally was greater than that observed with bilateral CO2/HCO3-. CO2/HCO3- only in the bath also reduced the lag time to approximately 51 s, which is not significantly different from the value of approximately 36 s observed with bilateral CO2/HCO3-. Our data are consistent with the hypothesis that basolateral (but not luminal) CO2/HCO3- stimulates both a luminal Na+/H+ exchanger and a luminal H+ pump.