Quinn D A, Honeyman T W, Joseph P M, Thompson B T, Hales C A, Scheid C R
Department of Physiology, University of Massachusetts Medical School, Worcester 01655.
Am J Respir Cell Mol Biol. 1991 Dec;5(6):586-91. doi: 10.1165/ajrcmb/5.6.586.
In blood vessels in the systemic circulation, the plasmalemmal Na+/H+ exchanger has been implicated in a variety of cellular functions, including the regulation of intracellular pH (pHi) and cell volume, and the response to smooth muscle mitogens. The role of this transport system in pulmonary vascular smooth muscle has not been explored. The present study examined the characteristics of Na+/H+ exchange in cultured guinea pig pulmonary artery smooth muscle cells. These cells were subjected to an acid load, and the recovery from acid loading was monitored using the fluorescent pH-sensitive dye 2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein (BCECF). In the absence of HCO3-, pHi recovery from acid loading was dependent on external Na+ and was inhibited by the Na+/H+ exchange inhibitor dimethylamiloride (DMA) (recovery rate was reduced from 54.4 +/- 5.5 to 12.8 +/- 2.0 mmol H+/liter.min). This exchanger was also active in the presence of HCO3-; DMA reduced resting pHi and slowed the rate of recovery from acid loading in HCO3- buffers. However, in the presence of HCO3-, other transport systems, presumably HCO3-/Cl- exchange, also contribute to the regulation of pHi. In HCO3- buffers, the rate of recovery from acid load averaged 40.8 +/- 1.8 mmol H+/liter.min. Addition of 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS), an inhibitor of HCO3-/Cl- exchange, slowed this recovery to 25.5 +/- 1.6 mmol H+/liter.min. A combination of DIDS and DMA further slowed the recovery to 19.7 +/- 1.5 mmol H+/liter.min. These findings indicate that the Na+/H+ exchanger plays a significant role in the regulation of pHi in pulmonary artery smooth muscle cells, even in HCO(3-)-containing buffers.
在体循环的血管中，质膜Na⁺/H⁺交换体参与多种细胞功能，包括细胞内pH（pHi）和细胞体积的调节，以及对平滑肌有丝分裂原的反应。该转运系统在肺血管平滑肌中的作用尚未得到研究。本研究检测了培养的豚鼠肺动脉平滑肌细胞中Na⁺/H⁺交换的特性。对这些细胞施加酸负荷，并使用荧光pH敏感染料2',7'-双（羧乙基）-5（6）-羧基荧光素（BCECF）监测酸负荷后的恢复情况。在没有HCO₃⁻的情况下，酸负荷后pHi的恢复依赖于细胞外Na⁺，并被Na⁺/H⁺交换抑制剂二甲基amiloride（DMA）抑制（恢复速率从54.4±5.5降至12.8±2.0 mmol H⁺/升·分钟）。即使在存在HCO₃⁻的情况下，该交换体也有活性；DMA降低了静息pHi，并减缓了在HCO₃⁻缓冲液中酸负荷后的恢复速率。然而，在存在HCO₃⁻的情况下，其他转运系统，可能是HCO₃⁻/Cl⁻交换，也参与了pHi的调节。在HCO₃⁻缓冲液中，酸负荷后的平均恢复速率为40.8±1.8 mmol H⁺/升·分钟。添加4,4'-二异硫氰基芪-2,2'-二磺酸（DIDS），一种HCO₃⁻/Cl⁻交换抑制剂，使该恢复速率减慢至25.5±1.6 mmol H⁺/升·分钟。DIDS和DMA的组合进一步将恢复速率减慢至19.7±1.5 mmol H⁺/升·分钟。这些发现表明，即使在含有HCO₃⁻的缓冲液中，Na⁺/H⁺交换体在肺动脉平滑肌细胞pHi的调节中也起着重要作用。
