NOS3 and hypertensive disorder: Endothelial NOS converts l-arginine into nitric oxide, causing relaxation of vascular smooth muscle (Vaziri and Ding 2001; Vaziri et al. 1999) and associations among eNOS genotypes, hypertension, lead exposure, and intracellular Ca2+ concentrations have been reported (Colombo et al. 2002; Sofowora et al. 2001).