Arterial Baroreflex Function in African Americans at Rest and During Exercise

University Of Texas Arlington, Arlington TX

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Abstract

DESCRIPTION (provided by applicant): African Americans are at higher risk than their Caucasian American counterparts for the development of hypertension with hypertension affecting over 40% of the African American adult population. In addition, hypertension-related deaths of African Americans are twice that of Caucasian Americans. Moreover, normotensive African Americans exhibit exaggerated blood pressure responses to exercise, as well as to various laboratory pressor stimuli (e.g., cold pressor testing), relative to Caucasian Americans. Despite the obvious concern of hypertension, as well as the aforementioned exaggerated blood pressure responses to exercise and various pressor stimuli, little is known regarding dynamic blood pressure control mechanisms (i.e., arterial baroreflex function) in African Americans. The goal of this proposal is to test the hypothesis that baroreflex function and related control mechanisms (e.g., cardiac, muscle sympathetic nerve activity, peripheral vascular responsiveness, etc.), are impaired in African Americans at rest and during exercise compared to age, gender and fitness-matched Caucasian American counterparts. Non-invasive, carotid baroreflex function curves will be utilized to investigate arterial baroreflex function at rest and during steady-state leg cycling exercise, as well as during static handgrip exercise. Furthermore, the interaction between the baroreflex and the metaboreflex on blood pressure control will be examined between racial groups using carotid baroreflex testing during post-exercise muscle ischemia (following static handgrip exercise). Within racial groups, normotensive (systolic blood pressure <120 and diastolic blood pressure <80 mmHg) and pre-hypertensive (systolic blood pressure 120-139 or diastolic blood pressure 80-89 mmHg) groups will be studied in an attempt to distinguish potential racial differences associated with the hypertension disease process prior to the development of hypertension. Findings from the proposed work will establish important data related to baroreflex function and associated control mechanisms in African Americans at rest and during exercise. Specifically, they will uncover the interaction between different blood pressure control mechanisms at rest, during dynamic and static exercise and during metaboreflex activation, improving the understanding of blood pressure regulation in African Americans and providing important insight in this population before the development of hypertension (as well as in Caucasian Americans). Findings from this proposal will provide preliminary data for investigation of genetic differences (i.e., polymorphisms) related to the development of hypertension with attention to baroreflex function and interaction with other blood pressure control systems (e.g., renin-angiotensin-aldosterone system) in African Americans. PUBLIC HEALTH RELEVANCE: Hypertension affects over 40% of the African American adult population and hypertension-related deaths of African Americans are twice that of Caucasian Americans. This work will directly relate to the health of a racial group that is at high risk for hypertension. Furthermore, findings from the proposed work will provide a pivotal `first-step'in the understanding of baroreflex function and associated control mechanisms in normotensive and pre-hypertensive African Americans at rest and during exercise, providing important insight in this population before the development of hypertension (as well as in Caucasian Americans).