REN and myocardial ischemia: Because acute myocardial ischemia (<60 min) upregulates the cardiac renin-angiotensin system and impairs coronary flow regulation (51, 52), it is speculated that the small elevation of local Ang II at sub-vasomotor levels in the heart during disease states may cause oxidative stress at the local microvascular domain and elicit focal vasoconstriction and myocardial ischemia secondary to the reduced NO bioavailability.