Silva P, Epstein J A, Myers M A, Stevens A, Silva P, Epstein F H
Life Sci. 1986 Feb 10;38(6):547-52. doi: 10.1016/0024-3205(86)90033-0.
In the rectal gland of the spiny dogfish (Squalus acanthias), chloride enters the cell via a cotransport system together with sodium and potassium in a 2 Cl-: 1 Na+: 1 K+ stoichiometry. The system is energized by the electrochemical potential for sodium directed into the cell. Sodium is extruded from the cell by Na-K-ATPase located on the basolateral cell membrane. Chloride leaks into the lumen following a favorable electrical gradient. Potassium is thought to recirculate across the basolateral cell membrane. Since barium ions inhibit the efflux of potassium from cells we used barium chloride to explore the role of potassium in the process of stimulated secretion of chloride by the gland. The secretion of chloride was stimulated with theophylline 2.5 X 10(-4)M and dibutyryl cyclic AMP 5 X 10(-5)M. Ba++ inhibited the secretion of chloride in a way that was reversible and dose dependent. The reduction in secretion was associated with a parallel fall in transglandular electrical potential. Inhibition was half maximal at a concentration of Ba++ of 10(-3)M. The reduction in efflux of potassium produced by Ba++ presumably decreases the potassium diffusion potential, thus reducing the electronegativity of the cell and dissipating the driving force for chloride across the apical cell membrane. Recirculation of K+ across the basolateral border of the cell would thus be essential for the maintenance of chloride secretion by the gland.
在棘鲨（Squalus acanthias）的直肠腺中，氯离子通过一个共转运系统与钠和钾一同进入细胞，其化学计量比为2 Cl⁻: 1 Na⁺: 1 K⁺。该系统由钠离子进入细胞的电化学势提供能量。钠离子通过位于基底外侧细胞膜上的钠钾ATP酶从细胞中排出。氯离子顺着有利的电势梯度泄漏到管腔中。钾离子被认为在基底外侧细胞膜上进行再循环。由于钡离子抑制钾离子从细胞中流出，我们使用氯化钡来探究钾离子在该腺体氯离子刺激分泌过程中的作用。用2.5×10⁻⁴M的茶碱和5×10⁻⁵M的二丁酰环磷酸腺苷刺激氯离子分泌。钡离子以可逆且剂量依赖的方式抑制氯离子分泌。分泌的减少与跨腺体电势的平行下降相关。在钡离子浓度为10⁻³M时，抑制作用达到半数最大效应。钡离子导致的钾离子流出减少可能会降低钾离子扩散电位，从而降低细胞的电负性，并消除氯离子跨顶端细胞膜的驱动力。因此，钾离子在细胞基底外侧边界的再循环对于维持该腺体的氯离子分泌至关重要。
