Developing a Comprehensive Blood Volume Budget for Amphibians

小行星9603025 两栖动物失水很快，必须补充水分以维持生命。 作为陆栖脊椎动物，它们失水和吸水的速度是其他脊椎动物的十倍。 由于水的周转率高，出现缺水的可能性更大（水的损失超过水的获得）。 自然选择有利于对周期性缺水的耐受性，这在两栖动物中，更多的陆地物种比水生物种具有更大的脱水耐受性。 两栖动物的脱水耐受性比哺乳动物高2 - 4倍。 因此，他们代表了一个很好的脊椎动物模型系统，以解开什么心血管机制是重要的脱水耐受性。 心血管系统必须处理脱水期间其体积的减少。 两栖动物补偿低血容量的能力在不同物种之间是不同的，与其他脊椎动物相比是显着的。 描述补偿血容量减少的机制的第一步是为两栖动物循环系统中的所有液体进入和液体损失途径制定预算。 PI计划为两种对脱水的耐受性和维持血容量的能力不同的种属开发此类血容量预算。 这需要量化通过肾脏、皮肤、膀胱、淋巴、肾造口和毛细血管泄漏的液体体积。 PI将描述各种交换途径中低容量和高容量条件下可能的流量范围。 PI还将研究这些液体运动途径的神经内分泌控制的某些方面。 这项工作将：1）提供第一个非哺乳动物的血容量预算; 2）提供第一次测量两栖动物的血管渗漏和顺应性; 3）提供预算的哪些方面与脱水耐受性相关的测试;以及4）增加对在脊椎动物进化中水生到陆生过渡中什么心血管适应是重要的理解。 ***

9603025 Hillman Amphibians lose water very quickly, which must be replenished to sustain life. As terrestrial vertebrates they consequently lose and gain water at ten times the rate of other vertebrates. There is a greater potential for water deficits to occur (water loss exceeds water gain) as a consequence of these high water turnover rates. Natural selection has favored tolerance to periodic water deficits, its in amphibians, with more terrestrial species having greater dehydration tolerance than aquatic species. Amphibians have a two to four fold greater dehydration tolerance than mammals. They consequently represent an excellent vertebrate model system to unravel what cardiovascular mechanisms are important in dehydration tolerance. The cardiovascular system must deal with a decrease in its volume during dehydration. The amphibians ability to compensate for low blood volume is different between different species and remarkable in comparison to other vertebrates. The first step in describing the mechanisms involved in compensating for a decrease in blood volume is to develop a budget for all the avenues of fluid entry and fluid loss in the amphibian circulatory system. The PI plans to develop such a blood volume budget for two species which differ in their tolerance to dehydration and ability to maintain blood volume. This entails quantifying the volume of fluid moving through the kidneys, skin, bladder, lymph, nephrostomes and leaks in the capillaries. The PI will describe the range of flows possible in low volume and high volume conditions across the various pathways of exchange. The PI will also investigate some aspects of the neuroendocrine control of these pathways of fluid movement. The work will: 1 ) provide the first non-mammalian blood volume budget; 2) provide the first measurements of vascular leakiness and compliance for amphibians; 3) provide a test of which aspects of the budget correlate with dehydration tolerance; and 4) increase understanding of what c ardiovascular adaptations were important in the aquatic to terrestrial transition in vertebrate evolution. ***