MODES OF OPERATION OF THE SODIUM PUMP

该项目的长期目标是提供一个完整的动力学 钠/钾泵的热力学描述，或 (Na+ K）ATP酶。 钠/钾泵存在于 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，流体 分泌、感觉传导、营养物质的次级运输和 其他离子等。泵的产电性质影响感官 适应、起搏器产生和突触调制。 的行动 洋地黄类药物对心脏的作用几乎可以肯定是通过 泵 人体内的钠泵消耗的钠 ATP在体内产生。 这项建议的具体目的是继续分析 各种模式之间的动力学和热力学关系 钠泵的操作，特别注意的影响， 细胞膜电位对电流和/或通量的影响 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。 操作模式为 除了正向和反向Na/K交换外， K/K交换、生电和电中性Na/Na 交换和通过反转电位的电压操作运动。 这些实验的结果将通过严格的最小二乘法进行检验 针对特定理论（但总是"最小"）模型的分析 泵。 电压敏感速率常数将解释为 Albers-Post格式中各步的Eyring势垒模型 钠/钾泵 这项工作选择的细胞是鱿鱼的一个巨大的神经纤维， 由于其非常大的尺寸，允许实验访问和离子， 通过内部透析技术进行生化控制，以及 如通过非常稳定的电压箝位电路的电控制。 泵介导的通量和电流将被定义为强心的 类固醇诱导同位素通量和电压钳持的变化 目前，分别。

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.