This proposal examines the impact of excess sodium intake on the genesis of geriatric hypertension. Sodium has been linked to the etiology of hypertension in experimental animals and man, and age-related changes in sodium handling may accentuate the effects on control of blood pressure in the elderly. The study will approach the problems in several directions. First, the identification of salt-sensitive hypertensive subjects will be carried out by monitoring blood pressure response to high salt intake. This protocol will also examine the response of renin, aldosterone, natriuretic factors, dopamine and the kidney to salt loading on the premise that elderly hypertensives cannot mount the appropriate hormonal and renal response to sodium excess. Secondly, the study will evaluate outpatient sodium intake and taste perception for salt in the geriatric population using dietary recall, 24 h urinary sodium excretion and special studies of salt taste including threshold concentration and pleasantness ratings. The premise of this protocol is that older subjects may have a higher exposure to salt loads and less taste perception of saltiness. Several defects in sodium transport in cells from hypertensive animals and man have been described; these abnormalities may be the mechanism whereby salt causes hypertension. The third part of the proposal is based on the possibility that aged cells have less capacity to transport sodium. Three red blood cell sodium transport pathways will be examined in geriatric hypertension. The sympathetic nervous system can influence sodium disposal and there are age-related reductions in baroreceptor function. Evidence suggests that reduced baroreceptor function can confer salt sensitivity, thus slopes of baroreceptor sensitivity will be correlated with sodium handling in salt-sensitive geriatric hypertensives. Fifty hypertensive subjects over 60 years will be studied on a constant high salt diet to identify salt-sensitive hypertension. Results of the outlined studies in the salt sensitive group will be compared to the nonsalt-sensitive hypertensives and 30 normotensive age-matched controls. Examination of all components of sodium regulation should detect age-related abnormalities in sodium handling that may serve as an important mechanisms in geriatric hypertension, resulting in greater efforts to implement nonpharmacologic, nutritional methods to control hypertension in the elderly.
