This research study evaluates the relationship between high blood pressure (hypertension), and overweight or weight gain. High blood pressure and overweight are frequently associated. Although it is commonly believed that overweight leads to blood pressure elevation, there is some evidence suggesting that increased blood pressure can lead to increased body weight as well. The purpose of this study is to investigate one of the ways by which high blood pressure may lead to excessive weight gain. We think that in hypertensives the ability of the tissues to burn off extra calories is reduced which, in turn, leads to increased storage of fat and that this problem with burning calories is due to overactivity of the sympathetic nervous system. The sympathetic nervous system controls several functions in the body including blood pressure, heart rate as well as the turnover of energy generated from food. This system is excessively activated in the early stages of hypertension. In this study, in order to reproduce the sympathetic stimulation, we will infuse a drug, isoproterenol, which will increase heart rate, blood pressure, respiratory and metabolic rate. The effect is similar to mild physical exercise and to emotional excitement. We expect to show that in patients with high blood pressure the responses to isoproterenol infusion (increase in heart rate and blood pressure as well as metabolic reactions) will be reduced compared to subjects with normal blood pressure. This would weaken one of the mechanisms by which the body prevents weight gain and ultimately lead to weight gain. Longstanding high blood pressure and obesity increase morbidity and mortality in all populations, particularly when associated. A better understanding of the mechanisms supporting this relationship would help in developing better forms of intervention and, ultimately, could have a positive impact on prevention of strokes and heart attacks.
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