Upregulation of Angiotensin II Type 2 Receptor and Limitation of Myocardial Stunning by Angiotensin II Type 1 Receptor Blockers during Reperfused Myocardial Infarction in the Rat

Background: We have previously shown that angiotensin II type 1 receptor blockers induce cardioprotection and upregulate angiotensin II type 2 receptor during in vivo postischemicreperfusion in dogs. Whether angiotensin II type 1 receptor blockers upregulate angiotensin II type 2 receptors in rats is controversial, and whether surmountable and insurmountable angiotensin II type 1 receptor blockers exert similar protective effects during reperfused myocardial infarction is not known.Methods: We assessed the effects of the surmountable angiotensin receptor blocker valsartan, and the insurmountable angiotensin receptor blocker irbesartan, on hemodynamics and left ventricular systolic and diastolic function (echocardiography/Doppler) in vivo and infarct size (triphenyl tetrazolium chloride method), and regional angiotensin II type 1 receptor and angiotensin II type 2 receptor expression (immunoblots) ex vivo, after anterior reperfused myocardial infarction in rats. The rats were randomized to four groups: int...