Cell Volume Regulation in Bivalves: Response to Fluctuating Salinity

9407997赖特由于海水中的盐分浓度非常高，海洋动物生活在持续的盐度压力下。海洋无脊椎动物通常通过在它们的细胞中保持一种无机溶质的组合来应对这种压力，这些无机溶质组合在一起平衡了全强度海水的大渗透浓度。生态无脊椎动物面临着额外的挑战。由于每天潮汐的变化，餐厅的环境可能会从最大强度的海水周期性地转变为淡水。因此，生活在潮间带栖息地的动物可能会暴露在环境渗透压的变化中，这可能会对它们的生理产生深远的影响。特别是，当暴露在渗透压降低(即稀释的海水)中时，食堂动物的细胞和组织通常会肿胀。人们普遍认为，细胞对这种类型的压力的反应包括溶质的损失，这会导致渗透压所致的水分损失，从而使体积减少到正常水平。事实上，这已经被证明是许多哺乳动物细胞的情况。对于每天面临渗透压大变化的生态动物来说，当潮汐变化和周围环境渗透压恢复正常时，任何溶质的损失都必须通过溶质的等量增加来弥补。尽管细胞溶质的这些循环损失和获得可能会给动物带来巨大的能量成本，但与暴露在循环中相关的能量压力的实际程度尚不清楚。本工作将研究盐度的周期性变化对(I)渗透诱导的细胞大小变化的程度；(Ii)伴随的细胞溶质浓度的变化；以及(Iii)对这些变化的调控反应的细胞机制的影响。这些实验将集中在双壳贝鳃对盐度胁迫的反应，这是一种独特的组织，适合使用直接光学和直接放射性示踪剂方法测量细胞体积。这一技术的结合将允许测量完整动物以及分离组织中的体积调节程度。拟议的研究结果将导致第一次评估细胞体积调节对食道动物能量收支的影响。

9407997 Wright Because of the very large concentrations of salt in seawater, marine animals live under constant salinity stress. Marine invertebrates generally cope with this stress by maintaining in their cells a combination of inorganic solutes that together balance the large osmotic concentration of full strength sea water. Estaurine invertebrates face an added challenge. As a consequence of the daily change in tides, the estaurine environment can cyclically shift from full strength sea water to freshwater. Animals living in the intertidal habitats can, therefore, be exposed to changes in ambient osmolarity that can have a profound impact on their physiology. In particular, when exposed to reduced osmolarity (i.e., dilute sea water), the cells and tissues of estaurine animals typically swell. It is widely believed that the response of cells to this type of stress includes a loss of solute that induces an osmotically-obligated loss of water and hence a reduction in volume back toward normal levels. Indeed, this has been shown to be the case for many mammalian cells. For an estaurine animal faced with large daily shifts in osmolarity, any loss of solute must be met by an equal gain in solute when the tide shifts and ambient osmolarity returns to normal. Although these cyclic losses and gains of cell solute could represent a substantial energy cost to the animal, the actual extent of the energetic stress associated with exposure to cycles is unknown. The present work will examine the influence of cyclic changes in salinity on (i) the extent of osmostically-induced changes in cell size; (ii) the accompanying changes in cell solute concentration; and (iii) the cellular mechanism of the regulatory response to these changes. The experiments will focus on the response to salinity stress of bivalve gills, a tissue uniquely suited to measurement of cell volume using both direct optical and direct radiotracer methods. This combination of techniques will permit measu rement of the extent of volume regulation in intact animals as well as in isolated tissues. The results of the proposed studies will lead to the first assessment of the impact of cell volume regulation on the energy budget of an estaurine animal.