Ziegelstein R C, Cheng L, Blank P S, Spurgeon H A, Lakatta E G, Hansford R G, Capogrossi M C
Laboratory of Cardiovascular Science, Gerontology Research Center, National Institute on Aging, National Institutes of Health, Baltimore 21224.
Am J Physiol. 1993 Oct;265(4 Pt 2):H1424-33. doi: 10.1152/ajpheart.1993.265.4.H1424.
Acidosis produces vasodilation in a process that may involve the vascular endothelium. Because synthesis and release of endothelium-derived vasodilatory substances are linked to an increase in cytosolic calcium concentration ([Ca2+]i), we examined the effect of intracellular acidification on cultured rat aortic endothelial cells loaded either with the pH-sensitive probe carboxy-seminaphthorhodafluor-1 or the Ca(2+)-sensitive fluorescent probe indo 1. The basal cytosolic pH (pHi) of endothelial monolayers in a 5% CO2-HCO3- buffer was 7.27 +/- 0.02 and that in a bicarbonate-free solution was 7.22 +/- 0.03. Acidification was induced either by removal of NH4Cl (delta pHi = -0.10 +/- 0.02), changing from a bicarbonate-free to a 5% CO2-HCO3(-)-buffered solution at constant buffer pH (delta pHi = -0.18 +/- 0.03), or changing from a 5% to a 20% CO2-HCO3- solution (delta pHi = -0.27 +/- 0.07). Regardless of the method used, intracellular acidification increased [Ca2+]i as indexed by indo 1 fluorescence. The increase in [Ca2+]i induced by changing from a 5 to a 20% CO2-HCO3- solution was not significantly altered by removal of buffer Ca2+ either before or after depletion of bradykinin- and thapsigargin-sensitive intracellular Ca2+ stores. Thus intracellular acidification of vascular endothelial cells releases Ca2+ into the cytosol either from pH-sensitive intracellular buffer sites, mitochondria, or from bradykinin- and thapsigargin-insensitive intracellular stores. This Ca2+ mobilization may be linked to endothelial synthesis and release of vasodilatory substances during acidosis.
酸中毒在一个可能涉及血管内皮的过程中产生血管舒张。由于内皮源性血管舒张物质的合成和释放与胞质钙浓度（[Ca2+]i）的增加有关，我们研究了细胞内酸化对用pH敏感探针羧基半萘罗丹明-1或Ca(2+)敏感荧光探针indo 1加载的培养大鼠主动脉内皮细胞的影响。在5% CO2-HCO3-缓冲液中内皮单层的基础胞质pH（pHi）为7.27±0.02，在无碳酸氢盐溶液中为7.22±0.03。通过去除NH4Cl（ΔpHi = -0.10±0.02）、在恒定缓冲液pH下从无碳酸氢盐溶液变为5% CO2-HCO3(-)缓冲溶液（ΔpHi = -0.18±0.03）或从5%变为20% CO2-HCO3-溶液（ΔpHi = -0.27±0.07）来诱导酸化。无论使用何种方法，细胞内酸化都会使由indo 1荧光指示的[Ca2+]i增加。从5%变为20% CO2-HCO3-溶液诱导的[Ca2+]i增加在缓激肽和毒胡萝卜素敏感的细胞内Ca2+储存耗尽之前或之后去除缓冲液Ca2+时均未发生显著改变。因此，血管内皮细胞的细胞内酸化会使Ca2+从pH敏感的细胞内缓冲位点、线粒体或从缓激肽和毒胡萝卜素不敏感的细胞内储存释放到胞质溶胶中。这种Ca2+动员可能与酸中毒期间内皮源性血管舒张物质的合成和释放有关。
