Purity >98%. Angiotensin II is a peptide hormone that regulates blood pressure and fluid balance, contributing to hypertension, atherosclerosis, left ventricular hypertrophy, myocardial infarction, and heart failure. It binds with high affinity to two distinct receptors: AT1 R (angiotensin type 1 receptor) and AT2 R (angiotensin type 2 receptor). AT1 R activation facilitates the 'classical' effects, including vasoconstriction, cellular growth, and proliferation, whereas AT2 R activation offsets AT1 R-mediated actions, promoting vasodilatation, apoptosis, and anti-growth effects. PD 123319 is a selective, nonpeptide AT2 R antagonist (IC50 = 5.6 nM vs. 100 nM for AT1 R). It has been used to selectively examine the specific roles for AT1 R and AT2 R in hypertensive and other vascular research-related models.