Moore L E
J Gen Physiol. 1969 Jul;54(1):33-52. doi: 10.1085/jgp.54.1.33.
Unidirectional chloride effluxes from small bundles of muscle fibers were measured under equilibrium conditions. It was found that chloride effluxes are described by the constant field theory with a chloride permeability constant, P(cl), which is independent of the chloride concentration and the membrane potential. The value of P(cl) at neutral pH was found to be 5 x 10(-6) cm/sec. Chloride movements were markedly depressed at low pH and increased at high pH. It is concluded that chloride fluxes are independent of each other over a wide pH range. The effect of nitrate on the chloride effluxes was measured. It was found that both external and internal nitrate alone reduced the chloride efflux with the external nitrate appearing more effective than internal nitrate due to the nonequilibrium nature of the experimental conditions. Under equilibrium conditions the reduction of the chloride efflux by nitrate was greater than the external nitrate effect, both of which were dependent on the relative proportion of nitrate in the bathing solution. These results are consistent with the hypothesis that the inhibition of the chloride movements by nitrate is essentially symmetrical with regard to the inside and outside surfaces of the muscle membranes. The relative action of nitrate on the chloride efflux was independent of the external pH despite marked changes in the absolute values of the fluxes measured.
在平衡条件下测量了小束肌纤维的单向氯离子外流。发现氯离子外流可用恒定场理论描述，其氯离子渗透常数P(cl)与氯离子浓度和膜电位无关。发现在中性pH值下P(cl)的值为5×10(-6)厘米/秒。在低pH值时氯离子移动明显受抑制，在高pH值时增加。得出结论，在很宽的pH范围内氯离子通量相互独立。测量了硝酸盐对氯离子外流的影响。发现单独的外部和内部硝酸盐都降低了氯离子外流，由于实验条件的非平衡性质，外部硝酸盐比内部硝酸盐更有效。在平衡条件下，硝酸盐对氯离子外流的降低大于外部硝酸盐的影响，两者都取决于浴液中硝酸盐的相对比例。这些结果与以下假设一致，即硝酸盐对氯离子移动的抑制在肌膜的内表面和外表面基本上是对称的。尽管测量的通量绝对值有明显变化，但硝酸盐对氯离子外流的相对作用与外部pH无关。
