NOS3 and hypertensive disorder: The vasodilator effect of NO that is produced by eNOS is very important for maintenance of vascular function [30], and the G894T polymorphism (Glu298Asp or rs1799983) at exon 7 of the eNOS gene is associated with reduced eNOS expression, activity and subsequently reduced NO production, could be a potential candidate marker for hypertension development [31, 32].