Renin angiotensin system (RAS) plays an important role in regulating blood pressure and body fluid balance. Angiotensin II, or AII, has two subtypes of AT1 and AT2. AT1 is a common RAS blocker. It has a strong specificity. AT1 receptors are mainly distributed in the heart and blood vessels, and also in the brain, kidneys and adrenal glands (mainly small bands of aldosterone). It can make AII constrict blood vessels and inhibit the release of aldosterone by epinephrine, thus it can reduce blood pressure, reduce heart load, and treat congestive heart failure effectly. It is essential for the balance of cardiovascular function in the body. In addition, AT1 also affects physiological activities related to hypertension, they include vasoconstriction, sodium/water retention, increasing the activity of sympathetic and promoting cell growth. AT2 can not regulate the balance of cardiovascular function. Losartan can bind to AT1 receptor highly and specifically , and the selectivity to AT1 receptor is 10 thousand times higher than that of AT2 receptor. Losartan
can inhibit AII in a single phase, and specifically bind to AT1 receptor site. And as a derivative drug, Losartan Potassium is also very important for patients.