Ishida Y, Takagi K, Urakawa N
J Physiol. 1984 Feb;347:149-59. doi: 10.1113/jphysiol.1984.sp015058.
When potassium (45.4 mM) was applied to isolated taenia of guinea-pig caecum, the muscle developed a rapid phasic and sustained tonic tension during aerobic conditions bubbled with 95% O2:5% CO2. Under hypoxic conditions bubbled with 95% N2:5% CO2, the taenia lost its ability to respond to high potassium with sustained tonic contraction, although it still showed rapid phasic contraction. Raising the glucose concentration from 5.5 to 55.5 mM in the presence of high potassium during hypoxia caused development of a sustained contraction which was 50% that of the muscle in aerobic conditions. In the presence of high potassium, the ATP content of the taenia decreased in hypoxia, but increased with increasing glucose concentration. When the taenia was exposed to hypoxic conditions, the amount of lactate released from the muscle increased. Raising the glucose concentration caused a further increase in lactate release in the presence of high potassium under hypoxia. Good correlations (gamma greater than 0.9) were observed between tension development, the ATP content and lactate release of the taenia in the presence of high potassium under hypoxia when the glucose concentration was varied between 5.5 and 55.5 mM. The total calcium content was increased by the presence of high potassium under aerobic conditions and the increase was abolished when the muscle was exposed to hypoxic conditions. Under hypoxia the total calcium content was not increased by raising the glucose concentration in the presence of high potassium. The cellular calcium content of the taenia, determined by the lanthanum method, was increased in the presence of high potassium under aerobic and hypoxic conditions, but the content was smaller in hypoxic conditions than in aerobic conditions. Under hypoxic conditions, raising the glucose concentration in the presence of high potassium did not affect the cellular calcium content. These results suggest that under hypoxic conditions the potassium-induced sustained contraction of the taenia is increased by raising the glucose concentration owing to increased ATP production through the glycolytic pathway, but not through mechanisms increasing the intracellular Ca concentration.
当向豚鼠盲肠离体绦虫施加钾离子（45.4 mM）时，在通入95% O₂:5% CO₂ 的有氧条件下，肌肉会产生快速的相性张力和持续的强直性张力。在通入95% N₂:5% CO₂ 的缺氧条件下，绦虫失去了对高钾产生持续强直性收缩的反应能力，尽管它仍表现出快速的相性收缩。在缺氧且存在高钾的情况下，将葡萄糖浓度从5.5 mM提高到55.5 mM会导致产生持续收缩，其强度为有氧条件下肌肉收缩强度的50%。在存在高钾的情况下，绦虫的ATP含量在缺氧时降低，但随葡萄糖浓度升高而增加。当绦虫暴露于缺氧条件时，肌肉释放的乳酸量增加。在缺氧且存在高钾的情况下提高葡萄糖浓度会导致乳酸释放进一步增加。当葡萄糖浓度在5.5至55.5 mM之间变化时，在缺氧且存在高钾的情况下，绦虫的张力产生、ATP含量和乳酸释放之间观察到良好的相关性（γ大于0.9）。在有氧条件下，高钾的存在会增加总钙含量，而当肌肉暴露于缺氧条件时，这种增加就会消失。在缺氧情况下，在存在高钾的情况下提高葡萄糖浓度并不会增加总钙含量。用镧法测定的绦虫细胞内钙含量在有氧和缺氧条件下存在高钾时都会增加，但在缺氧条件下的含量比有氧条件下小。在缺氧条件下，在存在高钾的情况下提高葡萄糖浓度不会影响细胞内钙含量。这些结果表明，在缺氧条件下，绦虫钾诱导的持续收缩会因通过糖酵解途径增加ATP生成而提高葡萄糖浓度而增强，但不是通过增加细胞内Ca浓度的机制。
