MODES OF OPERATION OF THE SODIUM PUMP

这个项目的长期目标是提供一个完整的动力 和钠/钾泵的热力学描述，或 (Na，K)ATPase。钠/钾泵存在于细胞膜 几乎所有的动物细胞，在那里它负责维持 跨膜Na和K梯度、容量和pH调节、液体 分泌，感觉转导，营养物质的第二次运输和 其他离子等。泵的生电性质影响感官 适应、起搏器的产生和突触的调节。行动 洋地黄药物对心脏的作用几乎可以肯定是通过钠 打气筒。人类体内的钠泵消耗了相当大一部分 体内制造的三磷酸腺苷。 这项建议的具体目的是继续分析 不同模式之间的动力学和热力学关系 钠泵的运行，特别要注意 细胞膜电位对电流和/或通量产生的影响 泵和动力学参数(个别速率常数；Km‘s；Ki’s； 希尔系数)控制它们。操作模式须为 被调查的除了向前和向后的Na/K交换外，还包括 K/K交换、生电和电中和Na/Na行为 交换，以及通过反转电位的电压操作运动。 这些实验的结果将用严格的最小二乘法进行检验 针对特定理论(但始终是“最小”的)模型的分析 打气筒。电压敏感的速率常数将被解释为 Albers-Post方案中各个步骤的Eyring-Blear模型 用于钠/钾泵。 为这项工作选择的细胞是鱿鱼的巨大神经纤维， 由于其非常大的尺寸，允许实验访问和离子和 通过内透析技术进行生化控制 由于电气控制采用了非常稳定的电压钳位电路。 泵调节的流量和电流将被定义为强心 类固醇引起的同位素通量变化与电压钳制 电流分别为。

The long-term objective of this project is to provide a complete kinetic and thermodynamic description of the sodium/potassium pump, or (Na+K)ATPase. The sodium/potassium pump is present in the membrane of nearly all animal cells, where it is responsible for maintenance of the transmembrane Na and K gradients, volume and pH regulation, fluid secretion, sensory transduction, secondary transport of nutrients and other ions, etc. The electrogenic nature of the pump affects sensory adaptation, pacemaker generation, and synaptic modulation. The action of digitalis drugs on the heart is almost certainly through the sodium pump. The sodium pump in man consumes an appreciable fraction of all ATP made in the body. The specific aims of this proposal are to continue the analysis of kinetic and thermodynamic relationships between the various modes of operation of the sodium pump, with special attention to the effect of cell membrane potential on the currents and/or fluxes generated by the pump, and the kinetic parameters (individual rate constants; Km's; Ki's; Hill coefficients) governing them. Modes of operation to be investigated include, besides forward and backward Na/K exchange, such behaviors as K/K exchange, electrogenic and electroneutral Na/Na exchange, and voltage-operated movement through reversal potential. Results of these experiments will be tested by rigorous least-squares analysis against specific theoretical (but always "minimal") models of the pump. Voltage-sensitive rate constants will be interpreted in terms of Eyring-barrier models for individual steps in the Albers-Post scheme for the sodium/potassium pump. The cell chosen for this work is a giant nerve fiber of the squid which, because of its very large size, allows experimental access and ionic and biochemical control by means of the internal dialysis technique, as well as electrical control by means a very stable voltage-clamp circuit. Pump-mediated fluxes and current will be defined as cardiotonic steroid-induced changes in isotope fluxes and voltage-clamp holding current, respectively.