Stanton Caitlin R, Thibodeau Renee, Lankowski Alexander, Shaw Joseph R, Hamilton Joshua W, Stanton Bruce A
Department of Physiology, Dartmouth Medical School, Hanover, Germany.
Cell Physiol Biochem. 2006;17(5-6):269-78. doi: 10.1159/000094139. Epub 2006 Jun 20.
Killifish are euryhaline teleosts that normally experience rapid changes in the salinity of the swim water. Acclimation to seawater is mediated by cortisol, which by activating glucocorticoid receptors, upregulates CFTR mediated Cl- secretion in the gill and operculum. Arsenic, a toxic metalloid that naturally occurs in the aquatic environment, has been shown to disrupt glucocorticoid hormone-mediated regulation of genes. Because little is known about the effects of environmentally relevant levels of arsenic on ion channels and salt homeostasis, studies were conducted to examine the effects of arsenic on the ability of killifish to acclimate to increased salinity. Arsenic in the swim water or administered by intraperitoneal injection prevented acclimation. To determine if arsenic blocked acclimation by inhibiting CFTR mediated Cl- secretion (Isc), opercular membranes were isolated and mounted in Ussing chambers and the effects of arsenic on Isc were measured. Arsenic (24 hr exposure) reduced Isc in opercular membranes isolated from salt water acclimated killifish. In addition, arsenic acutely (5-10 minutes) and reversibly inhibited Isc with an IC50 = 4.1 microM (305 ppb) when applied to the apical (seawater) side of the operculum, but not when added to the basolateral side of the operculum. Arsenic (4 microM for 60 minutes) also reduced mitochondrial respiration. Thus, environmentally relevant levels of arsenic block acclimation to seawater in killifish by reversibly inhibiting CFTR-mediated Cl- secretion by the opercular membrane, in part by inhibiting mitochondrial respiration.
鳉鱼是广盐性硬骨鱼，其游泳水体的盐度通常会迅速变化。对海水的适应是由皮质醇介导的，皮质醇通过激活糖皮质激素受体，上调鳃和鳃盖中CFTR介导的氯离子分泌。砷是一种在水生环境中天然存在的有毒类金属，已被证明会破坏糖皮质激素介导的基因调控。由于对环境相关水平的砷对离子通道和盐稳态的影响知之甚少，因此开展了研究以考察砷对鳉鱼适应盐度升高能力的影响。游泳水中的砷或通过腹腔注射给予的砷会阻止适应过程。为了确定砷是否通过抑制CFTR介导的氯离子分泌（Isc）来阻止适应，分离出鳃盖膜并安装在尤斯灌流小室中，测量砷对Isc的影响。砷（暴露24小时）降低了从适应盐水的鳉鱼分离出的鳃盖膜中的Isc。此外，当将砷应用于鳃盖的顶端（海水）侧时，它会急性（5 - 10分钟）且可逆地抑制Isc，IC50 = 4.1微摩尔（305 ppb），但添加到鳃盖的基底外侧时则不会。砷（4微摩尔，60分钟）也降低了线粒体呼吸作用。因此，环境相关水平的砷通过可逆地抑制鳃盖膜CFTR介导的氯离子分泌，部分是通过抑制线粒体呼吸作用，来阻止鳉鱼对海水的适应。
