Pichard C, Hoshino E, Allard J P, Charlton M P, Atwood H L, Jeejeebhoy K N
Division de Gastroenterologie et Nutrition, Hopital Cantonal Universitaire de Genève.
Am J Clin Nutr. 1991 Sep;54(3):489-98. doi: 10.1093/ajcn/54.3.489.
Nutrition alters total body potassium (TBK) and muscle potassium but little is known about in vivo intracellular K+. We measured free intracellular potassium-ion activity (aKi+), membrane potential (Em), and total potassium (Kt) and calculated intracellular potassium concentration [K+]i in predominantly slow- (soleus) and fast- (extensor digitorum longus) twitch muscles in rats undergoing underfeeding and subsequent refeeding. After underfeeding, aKi+ and Em decreased (P less than 0.025 and P less than 0.006, respectively) only in soleus muscle with restoration after refeeding, whereas [K+]i decreased in both muscles (P less than 0.005) and remained low after refeeding. K+ supplementation did not significantly change these indices or the ratio of free to total intracellular potassium (gamma Ki+). The data show that aKi+ behaves differently from [K+]i during malnutrition and that changes in aKi+ occur especially in slow-twitch fibers, suggesting that previously observed changes in TBK and muscle function are the result of fundamental alterations in muscle-cell energetics and membrane functions, not just mass.
营养状况会改变总体钾含量（TBK）和肌肉钾含量，但对于体内细胞内钾离子的情况却知之甚少。我们测量了自由细胞内钾离子活性（aKi+）、膜电位（Em）和总钾含量（Kt），并计算了接受饥饿及随后再喂养的大鼠中，主要为慢肌（比目鱼肌）和快肌（趾长伸肌）的细胞内钾浓度[K+]i。饥饿后，仅比目鱼肌中的aKi+和Em降低（分别为P<0.025和P<0.006），再喂养后恢复，而[K+]i在两块肌肉中均降低（P<0.005），再喂养后仍保持较低水平。补充钾并没有显著改变这些指标或细胞内自由钾与总钾的比例（γKi+）。数据表明，在营养不良期间，aKi+的表现与[K+]i不同，且aKi+的变化尤其发生在慢肌纤维中，这表明先前观察到的TBK和肌肉功能的变化是肌肉细胞能量代谢和膜功能发生根本改变的结果，而不仅仅是质量的变化。
