The Integrative Aspects of Fluid and Electrolyte Balance in Birds

提出的研究是研究两个器官系统如何整合来调节鸟类的液体和电解质。在哺乳动物中，肾脏的输出（尿液）被输送到一个储存器官——膀胱。这些尿液，一旦离开肾脏，就不会被修改。鸟类没有膀胱来储存尿液。相反，尿液由输尿管输送到胃肠道末端（泄殖腔）。尿液不会留在这里。它通过结肠肌层的反向作用进入结肠。在结肠中，肾脏形成的尿液可以被修改。鸟类的肾脏和结肠是如何整合成一个单位，以协调一致的方式维持液体和电解质平衡的，目前还不清楚。本提案中概述的研究旨在回答这个基本问题的某些方面。该提议的第二个方面涉及鸟类体内氮排泄的化学过程。哺乳动物（包括人类）以尿素的形式排出大部分废氮，这是一种水溶性很强的化合物。鸟类以尿酸的形式排出废氮，尿酸是一种非常不溶于水的化合物。以尿酸的形式排出氮可能会导致肾结石的形成，就像在人类身上一样。然而，鸟类排泄大量尿酸却不会形成肾结石。这是如何发生的还不清楚。这项拨款提案的一部分涉及旨在回答这个非常基本问题的研究。

The proposed research is to study how two organ systems are integrated to regulate fluid and electrolytes in birds. In mammals the output of the kidneys (the urine) is conveyed to a storage organ, the urinary bladders. This urine, once it leaves the kidneys is not modified. Birds do not have urinary bladders to store the urine. Instead the urine is conveyed by the ureters to the terminal segment of the gastrointestinal tract (the cloaca). The urine does not remain here. It is carried into the colon by a reverse action of the colonic muscle layers. In the colon, the urine formed by the kidneys can be modified. How the kidneys and colon of birds are integrated into a unit that functions in a concerted fashion to maintain the fluid and electrolyte balance is not understood. The research outlined in this proposal is directed toward answering some aspects of this basic question. A second aspect of the proposal deals with the chemistry of nitrogen excretion in birds. Mammals (including humans) excrete the majority of waste nitrogen as urea, a very water soluble compound. Birds excrete waste nitrogen in the form of uric acid, a very water insoluble compound. Excreting nitrogen as uric acid could lead to problems of kidney stone formation as it does in humans. However, birds excrete large amounts of uric acid without forming kidney stones. How this occurs is not understood. A portion of this grant proposal deals with research that is directed toward answering this very fundamental question.