Giunti Carine, Priouzeau Fabrice, Allemand Denis, Levraut Jacques
Unitè Mixte de Recherche INRA UNSA 1112, Rèponse des Organismes aux Stress Environnementaux, Nice, France.
Transl Res. 2007 Dec;150(6):350-6. doi: 10.1016/j.trsl.2007.05.002. Epub 2007 Jun 13.
The effect of Tris-Hydroxymethyl Aminomethane (THAM) on intracellular pH (pHi) is unknown. We previously demonstrated that the effect of sodium bicarbonate on pHi depends on the non-bicarbonate buffering system. First, human hepatocytes from hepatocytes cell culture (HepG2) were perfused with an acidotic artificial medium containing 5-mmol/L (H5) or 30-mmol/L (H30) concentrations of 4-(2-hydroxyethyl)-1-piperazineethane sulfonic acid (HEPES), a non-bicarbonate buffer. We studied the effect of THAM on the pHi in both conditions. We repeated the same protocol using an acidotic human blood with a 5% or 40% hematocrit. The pHi was measured with the pH-sensitive fluorescent dye bis-carboxyethyl carboxy-fluorescein (BCECF). Gas analysis was performed before and during the alkaline infusion. The results showed that THAM caused an intracellular alkalization that was higher when the non-bicarbonate buffer concentration was low (0.45 +/- 0.21 and 0.22 +/- 0.14 pH units with H5 and H30, respectively). A significant relationship was found between changes in pHi and changes in PCO(2). Similar results were obtained with the human blood. In conclusion, the intracellular alkalizing effect of THAM is caused by the induced decrease of PCO(2) linked to the extracellular non-bicarbonate buffer capacity: The smaller the concentration of extracellular non-bicarbonate buffer, the higher the PCO(2) decrease caused by THAM.
三羟甲基氨基甲烷（THAM）对细胞内pH值（pHi）的影响尚不清楚。我们之前证明了碳酸氢钠对pHi的影响取决于非碳酸氢盐缓冲系统。首先，用含有5 mmol/L（H5）或30 mmol/L（H30）浓度的4-（2-羟乙基）-1-哌嗪乙磺酸（HEPES，一种非碳酸氢盐缓冲剂）的酸性人工培养基灌注来自肝细胞培养物（HepG2）的人肝细胞。我们研究了在两种情况下THAM对pHi的影响。我们使用血细胞比容为5%或40%的酸性人血重复相同的实验方案。用pH敏感荧光染料双羧乙基羧基荧光素（BCECF）测量pHi。在碱性输注之前和期间进行气体分析。结果表明，THAM引起细胞内碱化，当非碳酸氢盐缓冲剂浓度较低时（分别为H5和H30时，pH单位分别为0.45±0.21和0.22±0.14），这种碱化作用更强。发现pHi的变化与PCO₂的变化之间存在显著关系。在人血中也获得了类似的结果。总之，THAM的细胞内碱化作用是由与细胞外非碳酸氢盐缓冲能力相关的PCO₂的诱导性降低引起的：细胞外非碳酸氢盐缓冲剂的浓度越小，THAM引起的PCO₂降低就越高。
