Dehydration is a stressor that may be encountered by many organisms during their lifetimes, including the period of body growth and organ development. Dehydration induces changes in hormone levels, including prominently increases in levels of anti-diuretic hormone, and the restricted water inhibits general body growth. Together, these factors may influence the growth and the development of many organ systems. The research will focus particularly on the effects of dehydration during growth on development of the kidney, a principle target organ for anti-diuretic hormone. The PI will study this problem in bobwhite quail, a species in which the chicks must forage for themselves beginning shortly after hatching, and in which therefore there is a very real possibility of dehydration during the early life stages. Preliminary data suggest that the region of the kidney (the renal medulla) primarily concerned with water conservation during dehydration hypertrophies when the birds are chronically water restricted. Associated with this is an enhanced ability to concentrate the urine, which should contribute to enhanced water conservation. The proposed research will further explore the functional consequences of chronic dehydration, and in particular will examine the basis for the enhanced concentrating ability. Does this reflect changes in the rate of urine formation, changes in hormone levels, or changes in the cellular response to the hormone? How do morphological changes induced by dehydration correlate with changes in function? Are these changes reversible, or do stresses imposed during youth have consequences that continue into adulthood? These studies will help to define the physiological responses of animals to dehydration. They will also examine the relation between structure and function in the avian kidney, about which much remains unknown or speculative. More generally, these studies will examine the flexibility of an important homeostatic system, and will address the general issue of the importance of environmental stresses on developmental pathways. This approach should identify constraints in design and function of the avian kidney. This relates both to the ability of individuals to acclimate to changing environments, as well as to the ability of species to invade and adapt to different habitats.
