Abstract-The prevalence of essential hypertension in blacks is much higher than that in whites. In addition, the pathogenesis of hypertension appears to be different in black patients. For example, black patients present with a salt-sensitive hypertension characterized by low renin levels. Racial differences in renal physiology and socioeconomic factors have been suggested as possible causes of this difference, but reasons for this difference remain unclear.Endothelial cells are important in the regulation of vascular tonus and homeostasis, in part through the secretion of vasoactive substances. One of these factors, endothelin-1 (ET-1), is a 21 amino acid residue peptide with potent vasopressor actions. In addition to its contractile effects, it has been shown to stimulate mitogenesis in a number of cell types. Moreover, ET-1 displays modulatory effects on the endocrine system, including stimulation of angiotensin II and aldosterone production and inhibition of antidiuretic hormone in the kidney. Recent data from several laboratories indicate that ET-1 is overexpressed in the vasculature in several salt-sensitive models of experimental hypertension. Moreover, circulating plasma ET-1 levels are significantly increased in black hypertensives compared with white hypertensives. Thus, the ET system might be particularly important in the development or maintenance of hypertension in this population. (Hypertension. 2000;36:62-67.)Key Words: endothelin Ⅲ hypertension, essential Ⅲ blacks Ⅲ sodium, dietary Ⅲ race E pidemiological studies have established that black Americans have an increased prevalence of essential hypertension compared with white Americans. [1][2][3][4] Furthermore, the disease onset is earlier, and the consequences of hypertension, which include heart failure, myocardial infarction, stroke, and renal failure, are more pronounced in black patients. 1,5 These racial differences in the development and clinical course of hypertension have been attributed to environmental and physiological factors. 1,5 One hypothesis is that the development and progression of hypertension in blacks are related to abnormal hemodynamic reactivity characterized by increased peripheral vascular resistance in response to external stimuli, including physical and mental stress. 1,6 Although the mechanism for increased peripheral vascular resistance has not been elucidated, vasoactive substances produced by endothelial cells such as endothelin-1 (ET-1) and NO are possible candidates to contribute to the vascular reactivity in response to mental stress. [7][8][9] An increase in ET-1 levels, the most potent vasoconstrictor peptide with growthpromoting properties, 10 a decrease in NO production, or both would shift the balance in favor of vasoconstriction. Moreover, recent studies suggest that ET-1 and its receptors are also involved in the regulation of sodium and water reabsorption and excretion and may contribute to the development or maintenance of salt-sensitive hypertension. 11,12 Interestingly, black patients with essential hy...