Since the discovery of “renin” in 1898 and subsequent recognition that AII is pressor, the RAS has been extensively studied and remains a major candidate as a causative factor in elevated arterial pressure and the pathogenesis of HT (Tigerstedt and Bergman 1898; de Gasparo et al. 2000; Carey and Siragy 2003). This evidence concerns the gene REN and hematocrit.