Department of Radiology, Box 357115, University of Washington Medical Center, Seattle, WA 98195-7115, USA.
J Appl Physiol (1985). 2010 Jun;108(6):1479-86. doi: 10.1152/japplphysiol.01189.2009. Epub 2010 Feb 4.
The link between lactate generation and cellular acidosis has been questioned based on the possibility of H+ generation, independent of lactate production during glycolysis under physiological conditions. Here we test whether glycolytic H+ generation matches lactate production over a physiological pH and lactate range using ischemia applied to the hindlimb of a mouse. We measured the H+ generation and ATP level in vivo using 31P-magnetic resonance spectroscopy and chemically determined intracellular lactate level in the hindlimb muscles. No significant change was found in ATP content by chemical analysis (P>0.1), in agreement with the stoichiometric decline in phosphocreatine (20.2+/-1.2 mM) vs. rise in Pi (18.7+/-2.0 mM), as measured by 31P-magnetic resonance spectroscopy. A substantial drop in pH from 7.0 to 6.7 and lactate accumulation to 25 mM were found during 25 min of ischemia. The rise in H+ generation closely agreed with the accumulation of lactate, as shown by a close correlation with a slope near identity (0.98; r2=0.86). This agreement between glycolytic H+ production and elevation of lactate is confirmed by an analysis of the underlying reactions involved in glycolysis in vivo and supports the concept of lactic acidosis under conditions that substantially elevate lactate and drop pH. However, this link is expected to fail with conditions that deplete phosphocreatine, leading to net ATP hydrolysis and nonglycolytic H+ generation. Thus both direct measurements and an analysis of the stoichiometry of glycolysis in vivo support lactate acidosis as a robust concept for physiological conditions of the muscle cell.
基于在生理条件下糖酵解过程中 H+ 的产生可能与乳酸生成无关的可能性，乳酸生成与细胞酸中毒之间的联系受到质疑。在这里，我们使用施加于小鼠后肢的缺血来检验在生理 pH 值和乳酸范围内糖酵解产生的 H+ 是否与乳酸生成相匹配。我们使用 31P 磁共振波谱学在体内测量 H+ 的生成和 ATP 水平，并通过化学方法测定后肢肌肉中的细胞内乳酸水平。化学分析未发现 ATP 含量有显著变化（P>0.1），与磷酸肌酸（20.2+/-1.2 mM）与 Pi（18.7+/-2.0 mM）的化学计量下降一致，后者通过 31P 磁共振波谱学测量。在 25 分钟的缺血过程中，pH 值从 7.0 显著下降至 6.7，乳酸积累至 25 mM。H+ 生成的增加与乳酸的积累密切一致，如通过接近单位斜率的密切相关性（0.98；r2=0.86）所示。糖酵解 H+ 生成与乳酸升高之间的这种一致性通过对体内糖酵解涉及的基本反应的分析得到证实，并支持在大幅度升高乳酸和降低 pH 值的条件下发生乳酸酸中毒的概念。然而，这种联系预计会在耗尽磷酸肌酸导致净 ATP 水解和非糖酵解 H+ 生成的情况下失效。因此，直接测量和对体内糖酵解的化学计量分析都支持乳酸酸中毒作为肌肉细胞生理条件下的一个稳健概念。
