Lower Intestinal and Renal Transport of Ammonia and Amino Acids in Birds: A Test of the Nitrogen Recycling Hypothesis

9870810莱弗蒂这项建议将寻求检验一些关于鸟类下肠道(结肠和盲肠)和肾脏之间存在假定的氮循环系统的预测。这项研究将具体检查与产氨底物的肠道和肾脏下部转运以及肾脏的氨化和分泌有关的方面。使用最近开发的禽类肾近端小管的原代细胞培养模型，将用类似的技术来研究肾脏的运输特性和氨化作用。这种培养系统在可渗透的过滤器支架上产生平坦、融合的近端细胞单层，显示出脊椎动物近端小管典型的形态、酶和运输特征。这些细胞释放氨的实际机制(管状分泌)将被研究，因为与哺乳动物不同的是，鸟类的近端小管不会在小管上皮细胞上产生pH梯度。此外，还将在模拟的酸化条件下测量氨基酸的摄取和氨化作用，将这些细胞培养置于酸性环境中。这些研究不仅将测试氮素循环系统的各个方面，还将提供有关禽类下肠道底物转运、肾脏氨基酸转运和肾脏氨化、分泌和对酸中毒的适应的新信息。这项拟议的工作将对进一步了解禽类下肠道功能、肾脏糖异生和肾脏酸碱生理学具有重要意义。

9870810 Laverty This proposal will seek to test some of the predictions of a postulated nitrogen recycling system between the lower intestine (colon and ceca) and kidney of birds. This study will examine the aspects specifically related to lower intestinal and renal transport of ammoniagenic substrates, as well as renal ammoniagenesis and secretion. Renal transport properties and ammoniagenesis will be studied by similar techniques, using a recently developed primary cell culture model of the avian renal proximal tubule. This culture system results in flat, confluent monolayers of proximal cells on permeable filter supports, which display morphological, enzymatic and transport characteristics typical of vertebrate proximal tubules. The actual mechanism of ammonia release (tubular secretion) from these cells will be examined, since avian proximal tubules, unlike their mammalian counterparts, do not generate pH gradients across the tubule epithelium. In addition amino acid uptake and ammoniagenesis will be measured under simulated acidotic conditions, y exposing these cell cultures to an acidic environment. These studies will not only test aspects of the nitrogen recycling system, but will also provide new information on avian lower intestinal substrate transport, renal amino acid transport and renal ammoniagenesis, secretion and adaptation to acidosis. The proposed work will be important in furthering an understanding of avian lower intestinal function, renal gluconeogenesis and renal acid-base physiology.