Stewart G W
Department of Pathology, Yale University School of Medicine, New Haven, Connecticut 06510.
Magnes Res. 1994 Jun;7(2):117-22.
It is a common clinical observation that changes in serum [K] are frequently associated with changes in serum [H] and/or [Mg]. Thus, hypokalaemia and alkalosis are associated, as are hyperkalaemia and acidosis, and hypokalaemia and hypomagnesaemia. Most investigators would accept that these ions have important roles in the maintenance of neuromuscular excitability. Extracellular potassium exerts its effect by defining the potassium gradient across the cell membrane and therefore the membrane potential in the resting state; magnesium and hydrogen ion 'screen' negative charges on the surface of nerve cells, modulating the local transmembrane potential gradient, to which the voltage-sensitive channels governing the initiation of the action potential respond. It is pointed out here that the changes in ionic concentration observed in pathophysiology are not incompatible with the idea that the associated changes reflect regulatory events in the extracellular fluid designed to preserve excitability.
临床上常见的观察结果是，血清[K]的变化常常与血清[H]和/或[Mg]的变化相关。因此，低钾血症与碱中毒相关，高钾血症与酸中毒相关，低钾血症与低镁血症也相关。大多数研究者会认同这些离子在维持神经肌肉兴奋性方面具有重要作用。细胞外钾通过确定跨细胞膜的钾梯度进而确定静息状态下的膜电位来发挥作用；镁离子和氢离子“屏蔽”神经细胞表面的负电荷，调节局部跨膜电位梯度，而控制动作电位起始的电压敏感通道对该电位梯度做出反应。这里需要指出的是，病理生理学中观察到的离子浓度变化与下述观点并不矛盾，即相关变化反映了细胞外液中旨在维持兴奋性的调节事件。
