Stress and diastolic dysfunction contribute to increased cardiovascular (CV) morbidity and mortality in hypertension. However, the relationship between these two mechanisms of CV disease is not well understood. We will employ an alternative theoretical model to the reactivity hypothesis which we refer to as the "pressure natriuresis" hypothesis. The focus of this model is on longer-term blood pressure (BP) control systems that maintain an increased pressure load within the heart for an extended period of time, increasing the likelihood of developing diastolic dysfunction. The specific aims of the proposed study are to test the following primary (1,2) and secondary hypotheses (3, 4, 5 and 6): (1) Stress will be associated with changes in the separate components (isovolumetric relaxation, early and late filling phases) of diastolic function (DFx). (2) The effect of stress on the components of DFx will differ by race and/or gender. (3) Stress- induced sodium excretion will correlate with concomitant stress-induced changes in DFx. (4) Stress-induced sodium excretion will correlate with concomitant stress-induced changes in natriuretic peptides (ANP, BMP). (5) Changes in BP during recovery (20-40 minutes post stress) will correlate with stress-induced changes in DFx. (6) Stress induced changes in catecholamines will be associated with changes in the components of DFx. The subjects population will consist of a bi-racial sample of 160 adults (African American, European American) aged 30-50 years. They will be placed on a controlled diet of sodium: 4,000+/-200 mg/day prior to testing. The experimental design is a two treatment, crossover design in which each subject receives both the experimental (mental stress task) and the control (watching a movie) treatments. The overall goal is to examine the role of psychological stress in the development of diastolic dysfunction. This will be the first comprehensive study to identify the role of natriuretic peptides in the stress-induced pressure natriuresis phenomenon and the link between pressure natriuresis and cardiac function in normotensive adults. Relevance to public health: The study will provide more efficacious early markers of cardiac malfunction before the development of overt signs of congestive heart failure. In so doing, it will contribute to development of population oriented prevention interventions that may help curb the epidemic spread of heart failure.