Shee C D, Cameron I R
Division of Medicine, United Medical School of Guy's Hospital, London, U.K.
Respir Physiol. 1990 Jan;79(1):57-68. doi: 10.1016/0034-5687(90)90060-c.
We studied the relationship between contractile function and intracellular pH (pHi) in the isolated rat diaphragm when superfusate PCO2 was changed during hyperoxia or hypoxia. Superfused diaphragm strips were field stimulated at 0.5 Herz, and twitch tension (TT) was recorded. The pHi was calculated from the volume distribution of a weak acid, dimethyl-oxazolidinedione. In hyperoxia, hypercapnic acidosis (pH 7.06-6.63) depressed diaphragm pHi and TT, whereas hypocapnic alkalosis (pH 7.82-8.15) increased pHi but did not significantly affect TT. TT was maximum at physiological pHi (7.06), but in hyperoxic hypercapnic muscles substantial force was still generated at pHi values as low as 6.44. Hypoxia (PO2 30-38 mm Hg) markedly reduced TT; this effect was slightly exacerbated by hypercapnia and attenuated by hypocapnia. Hypoxia lowered pHi by about 0.2 units, which was insufficient to account for the hypoxic contractile failure. Knowledge of the hyperoxic muscle TT/pHi relationship suggests that, in other contexts, caution should be exercised in attributing severe muscle fatigue or force loss to modest falls in pHi.
我们研究了在高氧或低氧期间改变灌流液PCO2时，离体大鼠膈肌收缩功能与细胞内pH值（pHi）之间的关系。对灌流的膈肌条以0.5赫兹进行场刺激，并记录抽搐张力（TT）。通过弱酸二甲基恶唑烷二酮的体积分布计算pHi。在高氧环境下，高碳酸血症性酸中毒（pH 7.06 - 6.63）会降低膈肌的pHi和TT，而低碳酸血症性碱中毒（pH 7.82 - 8.15）会升高pHi，但对TT没有显著影响。TT在生理pHi（7.06）时最大，但在高氧高碳酸血症的肌肉中，即使pHi低至6.44时仍能产生相当大的力量。低氧（PO2 30 - 38 mmHg）显著降低TT；高碳酸血症会轻微加剧这种作用，而低碳酸血症则会减弱这种作用。低氧使pHi降低约0.2个单位，这不足以解释低氧性收缩功能衰竭。高氧肌肉TT/pHi关系的知识表明，在其他情况下，将严重的肌肉疲劳或力量丧失归因于pHi的适度下降时应谨慎。
