Studies will be undertaken to define a role of the renin-angiotensin-aldosterone system in congestive heart failure, and to define the interactions of the autonomic nervous system, antidiuretic hormones, and renal prostaglandins. Studies will be performed in conscious dogs using three models - inferior vena cava constriction, pulmonary stenoisis, and aortic stenosis. To define events at the cellular level resulting from changes in these hormonal systems, studies will be performed to determine the changes in Na-K-ATPase distribution both in dogs and in rats and rabbits. Because urea hs been shown in preliminary experiments to result in changes in transmembrane potential differences of some kidney cells, studies will be performed to define the role of urea in tubular-glomerular feedback mechanisms.