Bentley P J, Maetz J, Payan P
J Exp Biol. 1976 Jun;64(3):629-37. doi: 10.1242/jeb.64.3.629.
The gills of the dogfish Scyliorhinus canicula are more permeable to Cl than to Na. In sea water, influx of Na and Cl exceeded the efflux of these ions. Under these conditions the fish were slightly electronegative, by about 2 mV, to the external solution. The net accumulation of Cl could be accounted for by diffusion along the observed electrochemical gradient byt the movement of Na into the fish was more consistent with an electrically neutral active Na transport mechanism (using the Ussing flux ratio criterion). When the external pH was was changed from 7-8 to 6-9,, influxes of Na and Cl were depressed, while the effluxes were unaffected, and the fish became slightly less electronegative. In artificial solutions, in which the concentrations of Na and Cl were lowered and replaced with urea to maintain the total osmotic concentration, Na influx displayed saturation kinetics, while Na efflux increased with decreasing Na concentrations. Cl influx decreased linearly, while Cl efflux remained constant. The efflux of Cl could not be reconciled with a process of passive diffusion along any of the observed electrochemical gradients and thus could reflect the presence of an active transport mechanism.
角鲨（Scyliorhinus canicula）的鳃对氯离子的通透性比对钠离子的通透性更高。在海水中，钠离子和氯离子的内流超过了这些离子的外流。在这些条件下，鱼相对于外部溶液略显电负性，约为2毫伏。氯离子的净积累可以通过沿观察到的电化学梯度的扩散来解释，但钠离子进入鱼体内的过程更符合电中性主动钠转运机制（使用乌斯辛通量比标准）。当外部pH值从7.8变为6.9时，钠离子和氯离子的内流受到抑制，而外流不受影响，鱼的电负性略有降低。在人工溶液中，降低钠离子和氯离子的浓度并用尿素替代以维持总渗透浓度，钠离子内流呈现饱和动力学，而钠离子外流随着钠离子浓度的降低而增加。氯离子内流呈线性下降，而氯离子外流保持恒定。氯离子的外流无法与沿任何观察到的电化学梯度的被动扩散过程相协调，因此可能反映了主动转运机制的存在。
