Endothelial dysfunction and a sedentary lifestyle may be involved in the development of hypertension which is proliferative among middle-aged African Americans (AA). Signaling molecules derived from the oxidation of 20-carbon fatty acid molecules known as eicosanoids influence vascular tone. The relationship between aerobic fitness and eicosanoid formation following exercise in middle-aged African American hypertensives is unknown. Purpose. To determine the relationship between aerobic capacity and eicosanoid formation after a bout of moderate-intensity exercise in middle-aged AA hypertensives. Methods. Ten sedentary hypertensive AA underwent 50？min of aerobic exercise at 65% VO2max. Urine was collected for 24 hr on two occasions, prior to testing and immediately following the bout of exercise. Urinary metabolites of prostacyclin (6-keto PGF1α) and thromboxane (11-dTXB2) were measured during the day and night periods by high-performance liquid chromatography (HPLC). Results. 6-keto PGF1α levels significantly increased ( ) following the bout of exercise compared to the control day. There was a significant relationship ( , ) between 6-keto PGF1α levels and VO2max during the exercise day. Conclusion. Based on this preliminary study, there appears to be a relationship between aerobic capacity and exercise-induced 6-keto PGF1α production in middle-aged hypertensive AAs. AAs with lower VO2max had lower 6-keto PGF1α formation. 1. Introduction Hypertension is a multifactorial disease that has high prevalence in African Americans [1, 2]. National surveys show that the majority of middle-aged, urban African Americans engage in little or no leisure-time physical activity [3]. This high prevalence of physical inactivity contributes to the disproportionate burden of obesity, hypertension, diabetes, and coronary heart disease in African Americans [3–5]. A number of important causal factors for hypertension have been identified. Research has implicated endothelial dysfunction as a factor involved in the pathogenesis of hypertension and is evident in the early stages of the development of coronary atherosclerosis [1, 6–9]. Hypertension is also more prevalent with advancing age. The prevalence of endothelial-impaired function disorders such as hypertension is disproportionately higher in the African American population in contrast to Caucasians [1, 2, 10]. Eicosanoids are 20-carbon molecules derived from arachidonic acid, a polyunsaturated fatty acid. Cyclooxygenase 1 or 2 (COX-1 or COX-2) and cell-specific synthases convert free arachidonic acid to a biologically
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