The Role and Regulation of Chloride Cells in Antarctic Fish

9613738南极佩泽尔鱼的血清渗透压是海水硬骨鱼中最高的。维持体液平衡对生存至关重要。在-1.5℃至4℃的温驯化过程中，通过挤压NaC1穿过鳃，鱼的血清渗透压降低了20%。鱼体内NaC1的挤出主要是由位于鳃弓和鳃盖上的分泌氯化物的细胞完成的。na1转运的驱动力是Na/ k - atp酶。迄今为止，没有关于南极鱼类血清渗透压升高的作用和调节的信息。由此产生的问题包括：氯离子细胞在盐挤压过程中起什么作用？哪些激素调节氯细胞的活性？本文将南极鱼类的氯离子细胞生理和调控与一种新西兰温性鱼类进行比较。拟开展的研究目标是在生理水平（通过研究离子转运活性）和分子水平（通过研究Na/ k - atp酶）上确定南极和新西兰鱼鳃功能的可塑性，具体而言，本研究将：1)确定南极鱼类热驯化时鳃Na/ k - atp酶活性增加的鳃挤压机制；2)确定激素对鳃挤压机制的调节。以前的研究表明，在南极鱼类变暖的情况下，由于鳃总Na/ k - atp酶水平的增加，NaC1挤压量增加。拟议的实验将测量氯化物细胞形态、代谢、生理和调节，同时测量增温和降温对整个鱼的影响。氯化物细胞形态的测量将包括在不同温度下细胞直径和数量的变化。为了确定Na/ k - atp酶在增温条件下介导盐挤压的作用，我们将测量总酶活性和总酶数。氯离子细胞在C1和Na运输中的作用将通过将鳃包膜上皮放置在使用室中来测定鱼升温对短路电流的影响，短路电流是氯离子通过氯离子细胞运输的直接测量。最后，氯细胞功能的调节将通过改变掌部皮质醇、催乳素和内源性内分泌水平来确定。拟议实验的结果将首次详细描述在南极鱼类中观察到的介导增强低渗透调节的潜在机制，并将这些结果与在新西兰常温鱼类中观察到的结果进行比较。

9613738 Petzel Antarctic fish have the highest serum osmolality of any seawater teleost. Maintenance of fluid balance is crucial for survival. Upon warm acclimation from -1.5o to 4oC the fish lmse 20% of their serum osmolality through extrusion of NaC1 across the gill. NaC1 extrusion in fish is primarily performed by chloride-secreting cells located on the gill arches and gill opercula. The driving force for NaC1 transport is the Na/K-ATPase. To date, no information is available concerning role and regulation of the elevated serum osmolarity in Antarctic fish. Questions which arise include: What role does the chloride cell play in mediating salt extrusion? Which hormones regulate chloride cell activity? The chloride cell physiology and regulation in Antarctic fish will be compared with a New Zealand fish which is eurythermal. The goals of the proposed research are to determine the plasticity of Antarctic and New Zealand fish gill function at the physiological level (through studies of ion transport activity) and molecular level (through studies of the Na/K-ATPase enzyme), specifically this research will: 1) determine the gill extrusion mechanisms underlying the increase in gill Na/K-ATPase activity upon warm acclimation in Antarctic fish and 2) determine the hormonal regulation of the gill extrusion mechanisms. Previously it was shown that upon warming of Antarctic fish there is an increase in NaC1 extrusion as a result of increases in gill total Na/K-ATPase enzyme levels. The proposed experiments will measure chloride cell morphology, metabolism, physiolmgy and regulation in parallel with effects of warming and cooling on the whole fish. Measurements of chloride cell morphology will include changes in diameter and number of cells at different temperatures. In order to ascertain the role of Na/K-ATPase in mediating the enhanced salt extrusion upon warming, we will measure total enzyme activity and total number of enzymes. The role of the chlor ide cell in transport of C1 and Na will assayed by placing the gill opercula sheet epithelia in Using chambers to determine the influence of fish warming on short-circuit current, which is a direct measurement of chloride transport through chloride cells. Finally, regulation of chloride cell function will be determined by altering palsma levels cortisol, prolactin and endogenous endocrines. The results from the proposed experiments will, for the first time, describe in detail the underlying mechanism(s) mediating the enhance hypo-osmoregulation observed in Antarctic fish and will allow the comparison of these results to those observed in a eurythermal New Zealand fish.