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.
