Urea Cycle and Pyrimidine Synthesis in Elasmobranchs

板鳃类（鲨鱼，冰鞋和光线）是一组原始的 鱼的组织中合成并保留高水平的 尿素的目的是抵消高盐 海水浓度。 我们的研究表明， 鲨鱼的尿素合成途径与 哺乳动物中的尿素循环，排泄氮废物 产品如尿素。 其他重大差异相关 也发现了代谢途径。 的目的 这项研究是为了1）表征这些独特的性质， 将结果与适应性代谢策略联系起来， 板鳃类和神经调节，2）将这些独特的 鲨鱼的新陈代谢特性。 结果将有助于 了解代谢适应和进化， 尿素合成不同途径的意义 相对于海水环境中渗透压的调节。

Elasmobranchs (sharks, skates, and rays) are a group of primitive fishes which synthesize and retain in their tissues high levels of urea for the purpose of counteracting the high salt concentration of seawater. Our studies have shown that the pathway for urea synthesis in sharks is uniquely different from the urea cycle in mammalian species, which excrete nitrogen waste products as urea. Other significant differences in related metabolic pathways have also been discovered. The purpose of this study is to 1) characterize these unique properties and relate the results to the adaptive metabolic strategies of elasmobranchs and osmoregulation and 2) relate these unique metabolic properties of the sharks. The results will contribute to understanding of metabolic adaptation and evolution, and of the significance of the different pathway for urea synthesis relative to regulation of osmolarity in a seawater environment.