DiPolo R, Rojas H
Biochim Biophys Acta. 1984 Oct 3;776(2):313-6. doi: 10.1016/0005-2736(84)90220-7.
The effect of external and internal K+ on Na+o-dependent Ca2+ efflux was studied in dialyzed squid axons under constant membrane potential. With axons clamped at their resting potentials, external K+ (up to 70 mM) has no effect on Na+-Ca2+ exchange. Removal of Ki+ causes a marked inhibition in the Na+o-dependent Ca2+ efflux component. Internal K+ activates the Na+-Ca2+ exchange with low affinity (K 1/2 = 90 mM). Activation by Ki+ is similar in the presence or in the absence of Na+i, thus ruling out a displacement of Na+i from its inhibitory site. Axons dialyzed with ATP also show a dependency of Ca2+ efflux on Ki+. The present results demonstrate that Ki+ is an important cofactor (partially required) for the proper functioning of the forward Na+-Ca2+ exchange.
在恒定膜电位下，研究了外部和内部钾离子对透析乌贼轴突中钠依赖型钙离子外流的影响。将轴突钳制在静息电位时，外部钾离子（高达70 mM）对钠钙交换没有影响。去除内部钾离子会显著抑制钠依赖型钙离子外流成分。内部钾离子以低亲和力（K1/2 = 90 mM）激活钠钙交换。无论有无内部钠离子，内部钾离子的激活作用相似，因此排除了内部钠离子从其抑制位点被置换的可能性。用ATP透析的轴突也显示钙离子外流对内部钾离子的依赖性。目前的结果表明，内部钾离子是正向钠钙交换正常运作的重要辅助因子（部分必需）。
