CADMIUM, COBALT, NICKEL EFFECT ON SIGNAL TRANSDUCTION IN SHARK RECTAL GLAND

该应用程序寻求膜毒理学中心的支持 沙漠山岛生物实验室（Mount Desert Island Biological Laboratory） 三种重金属（镉、钴和镍）的影响研究 激素调节氯分泌的信号转导途径 在鲨鱼的直肠腺里鲨鱼的直肠腺是一个同质的， 细胞类型，高度特化的上皮细胞，是一个模型系统， 激素调节氯化物分泌。 我们的假设是 重金属的影响是由于不同的特定的相互作用， 与抑制性激素信号相反的刺激性激素信号位点 转导途径。 我们已经确定，镉可逆地阻止 受体介导的氯分泌抑制， 这种效应的一个组成部分是通过一种新的和意想不到的机制发生的， 对刺激性激素的反应增强。 我们将确定 这种金属-蛋白质相互作用的特定位点， 镉对（a）镉的细胞外受体 介导三磷酸肌醇的活化和 细胞内钙;（B）对环化酶特异性同工酶的直接影响 核苷酸磷酸二酯酶;和（c）后受体/激酶机制- DFTR-氯离子通道从细胞内位点转运到 顶端质膜 与Cd相反，钴和镍抑制VIP 和毛喉素刺激灌注直肠腺中的氯化物分泌。 与中心其他人合作，我们将确定蛋白质 这些金属的相互作用位点，并区分毒性效应 对钙信使系统的影响和对心尖DFTR的直接作用 渠道 研究将在体外灌注直肠 直肠腺细胞的原代培养单层， 表达DFTR氯离子通道的非洲爪蟾卵母细胞。

This application seeks support through the Center for Membrane Toxicology Studies (CMTS) at the Mount Desert Island Biological Laboratory for studies on the effects of three heavy metals (cadmium, cobalt and nickel) on signal transduction pathways of hormones regulating chloride secretion in the shark rectal gland. The shark rectal gland is a homogenous, single cell type, highly specialized epithelium that is a model system for hormone regulated chloride secretion. Our hypothesis is that the toxic effects of heavy metals results from interactions at different specific sites of stimulatory as opposed to inhibitory hormonal signal transduction pathways. We have determined that cadmium reversibly blocks receptor-mediated inhibition of chloride secretion and that a major component of this effect occurs by a novel and unexpected mechanism- and augmentation of the response to stimulatory hormones. We will determine the specific site(s) of this metal-protein interaction by distinguishing between effects of cadmium on (a) an extracellular receptor for Cd mediating activation of inositol triphosphates and release of intracellular calcium; (b) direct effects on specific isozyme of cyclic nucleotide phosphodiesterases; and (c) a post-receptor/kinase mechanism- translocation of DFTR-chloride channels from an intracellular site to the apical plasma membrane. In contrast to Cd, cobalt and nickel inhibit VIP and forskolin stimulated chloride secretion in the perfused rectal gland. In collaboration with others in the center we will determine the protein interactive site(s) of these metals and distinguish between toxic effects on the calcium messenger system and direct actions on apical DFTR channels. Studies will be carried out in the in vitro perfused rectal gland, in primary culture monolayers of rectal gland cells, and in Xenopus oocytes expressing the DFTR chloride channel.