Ishibashi K, Sasaki S, Shiigai T, Takeuchi J
Jpn J Physiol. 1986;36(4):671-81. doi: 10.2170/jjphysiol.36.671.
Cortical collecting ducts (CCD) and inner stripe of outer medullary collecting ducts (OMCD) of the rabbit were perfused in vitro and the electrical potential was measured with 0.5 M KCl-filled conventional microelectrodes. In CCD, the transepithelial potential (Vte) was -1.9 +/- 0.5 (S.E.) mV and the intracellular potential (Vb) was -74.5 +/- 1.3 mV, while in OMCD, Vte was +2.0 +/- 0.4 mV and Vb was -24.6 +/- 1.0 mV. Acute reduction of peritubular HCO3- concentration from 25 to 5 mM (from pH 7.4 to 6.9) decreased Vb slowly but markedly from -26.3 +/- 1.8 to -18.9 +/- 1.6 mV (p less than 0.001) in OMCD, while it depolarized Vb slightly in CCD (from -75.6 +/- 1.9 to -74.3 +/- 2.1 mV, P less than 0.05). Acute peritubular pH reduction with HCO3- -free HEPES-buffered solution also depolarized Vb of OMCD from -24.7 +/- 2.1 to -15.9 +/- 1.6 mV (p less than 0.001). Although the mechanism(s) of Vb depolarization in OMCD is unclear at the moment, this depolarization suggests that OMCD is responsive to peritubular pH alterations. The results of this study provide the evidence that the collecting duct is heterogeneous in Vb values and its response to the peritubular pH change.
对家兔的皮质集合管（CCD）和外髓集合管内带（OMCD）进行体外灌注，并用填充0.5M KCl的传统微电极测量电位。在CCD中，跨上皮电位（Vte）为-1.9±0.5（标准误）mV，细胞内电位（Vb）为-74.5±1.3 mV，而在OMCD中，Vte为+2.0±0.4 mV，Vb为-24.6±1.0 mV。将管周HCO3-浓度从25 mM急性降低至5 mM（pH从7.4降至6.9），使OMCD中的Vb从-26.3±1.8 mV缓慢但显著降低至-18.9±1.6 mV（p<0.001），而在CCD中Vb略有去极化（从-75.6±1.9 mV降至-74.3±2.1 mV，P<0.05）。用不含HCO3-的HEPES缓冲溶液急性降低管周pH值也使OMCD的Vb从-24.7±2.1 mV去极化至-15.9±1.6 mV（p<0.001）。尽管目前尚不清楚OMCD中Vb去极化的机制，但这种去极化表明OMCD对管周pH值变化有反应。本研究结果提供了证据，表明集合管在Vb值及其对管周pH值变化的反应方面是异质性的。
