The Integrative Control of Fluid and Electrolyte Balance in Birds

[906431]在哺乳动物（人类）中，肾脏是唯一能维持血浆成分恒定的器官。维持血浆的成分是身体细胞正常运作所必需的。在鸟类中，血浆成分的调节情况略有不同。这主要是因为鸟类没有膀胱来储存尿液，直到尿液可以方便地排空，鸟类排出的氮以尿酸的形式排出，而不是像哺乳动物那样以尿素的形式排出。为什么鸟类和哺乳动物会有这种不同呢？为了更好地了解鸟类的肾脏功能，可以给出几个原因或理由。首先，鸟类（家禽）具有重要的经济意义，其次，对鸟类的研究可以获得对人类健康的见解。本提案的研究旨在解决鸟类如何调节其血浆葡萄糖浓度，鸟类如何以尿酸的形式排出大量氮而不形成肾结石，以及鸟类如何通过产生溶质浓度高于血浆浓度的尿液来保存体内水分。人的血浆葡萄糖浓度通常受到非常密切的调节（正常为80- 100mg %）。如果这一浓度增加到120-150毫克%，并长期保持在这一水平，II型相反，鸟类（家养）家禽的血浆葡萄糖浓度在正常情况下约为350毫克%。尽管浓度很高，但他们没有表现出II型糖尿病的症状。该提案的一部分研究将直接用于了解鸟类如何在高血浆葡萄糖浓度下生存。这个问题的答案可能有助于理解为什么人类会患上II型糖尿病。鸟类体内75%的氮以尿酸的形式排出体外。为什么这很有趣？尿酸几乎不溶于水，从浓度很低的溶液中析出。如果人体尿液中的浓度超过尿酸的溶解度限制，就会形成晶体。这些都会导致肾结石的形成。鸟类的尿液中含有高浓度的尿酸，但不会形成肾结石。关于这个提案的一部分研究将直接用于理解这种差异。鸟类有更简单的机制（但与哺乳动物相似）来浓缩尿液以保存体内水分。因为鸟类的这个系统不那么复杂，所以更容易研究和操作。这些研究的结果将有助于我们更好地理解哺乳动物（人类）的这个系统是如何运作的。总的来说，这项研究不仅为鸟类，也为哺乳动物（人类）的肾脏功能提供了更好的信息。

9906431BraunIn mammals (humans) the kidney is the only organ that functions to maintain the composition of plasma constant. It is necessary to maintain the composition of the plasma for the cells of the body to function in a normal manner. In birds, the situation with respect to the regulation of the composition of the plasma is slightly different. This is mainly because birds do not have a urinary bladder in which to store urine until it can be conveniently voided and birds excrete nitrogen as uric acid and not as urea as is the case for mammals. Why is this difference between birds and mammals of interest? Several reasons or justifications can be given for gaining a better understanding of kidney function in birds. First, birds (domestic fowl) are of a significant economic importance and second, human health insights can be gained from studies on birds. The research in this proposal is to address how birds regulate their plasma glucose concentration, how birds excrete large amount of nitrogen as uric acid without forming kidney stones, and how birds can conserve body water by producing urine in which the solutes are in a greater concentration than in the plasma. The plasma glucose concentration in humans is normally regulated very closely (normal is 80-100 mg%). If this concentration increases to 120-150 mg% and stays at these levels for a prolonged time, type II contrary, birds (domestic) fowl have plasma glucose concentrations of about 350 mg% as a normal circumstance. Despite these concentrations, they show no symptoms of type II diabetes. A portion of the research on this proposal will be directed toward understanding how birds live with these high plasma glucose concentrations. Answer(s) to this question may help in understanding why humans develop type II diabetes. Birds excrete 75% of their nitrogen as uric acid. Why is this of interest? Uric acid is almost insoluble in water and precipitates from solutions at very low concentrations. If the concentration in human urine exceeds the solubility limits of uric acid, crystals will form. These will lead to kidney stone formation. Birds have very high concentrations of uric acid in their urine, but do not form kidney stones. A portion of the research on this proposal will be directed toward understanding this difference. Birds have much simpler mechanism (but similar to mammals) to concentrate the urine to conserve body water. Because the system is less complicated in birds, it is much easier to study and manipulate. Results from these studies should lead to a better understanding of how the system functions in mammals (humans). Taken as whole, the proposed research should provide better information on kidney function not only in birds, but also in mammals (humans).