Juel Carsten
Copenhagen Muscle Research Centre, Department of Molecular Biology, University of Copenhagen, Universitetsparken 13, DK-2100, Denmark.
Appl Physiol Nutr Metab. 2007 Oct;32(5):846-51. doi: 10.1139/H07-065.
The analysis of blood samples has clearly demonstrated that exercise is associated with the release of K+ and H+ from muscle. However, blood samples give only incomplete information about the ion changes in the muscle interstitium. Interstitial changes in ion composition may affect the transport properties of the sarcolemmal membrane, may affect fibre excitability and induce fatigue, and may affect sensory nerve endings. Therefore, to better understand muscle function, it is important to quantify the exercise-induced interstitial ion changes. Both interstitial K+ and H+ changes have been quantified with the microdialysis technique. Interstitial K+ accumulation is dependent on the intensity and duration of muscle activity and may reach 10 mmol/L during intense exercise, and the concentration in T-tubules may be even higher. Thus, interstitial K+ can reach a level that affects fibre excitability and the development of fatigue. It has also been demonstrated with microdialysis that the interstitial decrease in pH during muscle activity is larger than the reduction in blood pH. Ion changes in the interstitium may affect blood flow directly or indirectly. Infusion of K+ into the femoral artery in humans has demonstrated that blood flow is affected by changes in K+ as low as 0.1 mmol/L. The vasodilatory effect of K+ can be inhibited with simultaneous barium infusion, indicating that inward rectifier potassium (Kir)channels are involved. Acidosis has a direct effect on blood flow and an indirect effect, mediated by changes in other vasoactive compounds.
血液样本分析清楚地表明，运动与肌肉中钾离子（K+）和氢离子（H+）的释放有关。然而，血液样本只能提供关于肌肉间质中离子变化的不完整信息。离子组成的间质变化可能会影响肌膜的转运特性，可能会影响纤维兴奋性并导致疲劳，还可能会影响感觉神经末梢。因此，为了更好地理解肌肉功能，量化运动引起的间质离子变化很重要。间质中K+和H+的变化都已通过微透析技术进行了量化。间质K+的积累取决于肌肉活动的强度和持续时间，在剧烈运动期间可能达到10 mmol/L，而横管中的浓度可能更高。因此，间质K+可以达到影响纤维兴奋性和疲劳发展的水平。微透析还表明，肌肉活动期间间质pH值的下降大于血液pH值的下降。间质中的离子变化可能直接或间接影响血流。在人体股动脉中注入K+已表明，低至0.1 mmol/L的K+变化就会影响血流。同时注入钡可抑制K+的血管舒张作用，表明内向整流钾（Kir）通道参与其中。酸中毒对血流有直接影响，并且通过其他血管活性化合物的变化介导产生间接影响。
