9630630 Goldstein The kidney is the organ fundamentally responsible for regulation of water and salt balance in birds. As in other vertebrate groups, these are regulated by a number of hormones. Studies of whole animals have elucidated a basic picture of some of these mechanisms. For regulation of water balance, the hormone arginine vasotocin (AVT, released from the pituitary gland of the brain) is primarily responsible for reducing urine flow. For regulating the balance of phosphate (a principle component of bone), the hormone parathyroid hormone (PTH, from the parathyroid glands in the neck) is primarily responsible for stimulating urinary excretion of phosphate. Yet the sites of action of these hormones (or, in fact, of any hormone) within the avian kidney are unknown. The avian kidney consists of thousands of individual functional units, the renal tubules. Within each kidney are two major subclasses of tubule, and within each tubule are several differently specialized regions. In the present studies, the PI will evaluate the specific site of aciton of AVT and PTH within the renal tubules. Adequate regulation of water and phosphate excretion are of basic value to survival; disruptions in these processes can lead to a variety of pathologies (e.g., kidney stones, a common disease of poultry). The present studies should lead to an improved understanding of the mechanisms which regulate these basic aspects of avian physiology.
