Specific Aim #5 is to study why different values are obtained when urinary kallikrein of Dahl's S rats is measured by direct RIA than when measured by kininogenase activity. For this, we will determine whether the inactive kallikrein measured by direct RIA is kallikrein bound to inhibitors or whether it is a prekallikrein. In addition, we will study how S and R rats' urinary kallikrein respond to changes in sodium intake. Specific Aim #6 is to explore the role of the sympathetic nervous system in the regulation of kallikrein excretion. For this, we plan (a) to study the effects of renal nerve stimulation on renal kallikrein release and then, if any, to study the effect of alpha and beta blockers; (b) to study the effect of intravenous and intrarenal infusion of catecholamines on kallikrein release. These two methods of infusion will be used since it has been reported that intravenous infusion of catecholamines is more effective than intrarenal in the stimulation of renin release (111,112); (c) to study the effect of dopamine and its antagonists on kallikrein release; and (d) to study if the acute increase in kallikrein release produced by Furosemide is altered by either denervation or adrenergic blockers.