Neurohormonal Control of Cellular Volume Regulation in Molluscs

本项目的目标是阐明海洋双壳软体动物细胞体积调节的神经激素控制机制。两种神经产物，FMRFamide和递质5-羟色胺(5HT)，增加了低渗胁迫下南方文蛤离体脑室的氨基酸外流。佛波酯还能增强低渗介质中组织的氨基酸外流，提示蛋白激酶C的激活参与了低渗容调节的控制。在低渗介质中，细胞内钙离子水平的变化在调节组织氨基酸外流中的作用将被研究。将测定暴露在低渗介质中的组织中蛋白激酶C活性的变化。还将使用免疫细胞化学技术研究内脏神经节中的神经分泌细胞因环境盐度下降而将FMRFamide释放到循环中的可能性。虽然神经激素与控制无脊椎动物的盐分和水分平衡有关，但目前还没有已知的激素与特定的渗透调节机制的控制明确相关。该项目将把FMRFamide的神经分泌与软体动物低渗细胞体积调节的控制联系起来。此外，该项目将提供有关软体动物和其他动物体积调节的细胞机制的新信息。

The goals of this project are to elucidate the mechanisms of neurohormonal control of cellular volume regulation in marine bivalve molluscs. Two neural products, the peptide FMRFamide and the transmitter 5-hydroxytryptamine (5HT) increase the efflux of amino acids from isolated ventricles of the clam Mercenaria mercenaria exposed to hypoosmotic stress. Phorbol esters also potentiate the amino acid efflux of tissues in hypoosmotic media, suggesting that the activation of protein kinase C is involved in the control of hypoosmotic volume regulation. The roles of changes in intracellular Ca++ levels in the modulation of the amino acid efflux of tissues in hypoosmotic media will be investigated. Changes in the activity of protein kinase C in tissues exposed to hypoosmotic media will be determined. The possibility that neurosecretory cells in the visceral ganglion release FMRFamide into the circulation in response to decreases in ambient salinity will also be investigated using immunocytochemical techniques. While neurohormones have been implicatead in the control of salt and water balance in invertebrates, no known hormone has yet been clearly associated with the control of a specific osmoregulatory mechanism. This project will associate the neurosecretion of FMRFamide with the control of hypoosmotic cellular volume regulation in molluscs. In addition, this project will provide new information on the cellular mechanisms involved in volume regulation in molluscs and other animals.