PO-09 SPIRONOLACTONE AS ADD-ON THERAPY TO CHLORTHALIDONE IMPROVES ENDOTHELIAL FUNCTION, ARTERIAL STIFFNESS AND INSULIN RESISTANCE IN EUROPEAN AND AFRICAN AMERICAN PATIENTS WITH ESSENTIAL HYPERTENSION – A DOUBLE-BLIND PLACEBO-CONTROLLED RANDOMIZED STUDY - T. Dudenbostel; T. Whigham; R. Pisoni; M.C. Acelajado; D.A. Calhoun (Artery Research, 2014)