type 1 angiotensin II receptor, member of the class A family of seven-transmembrane G protein-coupled receptors
Angiotensin II (Ang II), the main effector in the renin-angiotensin system, plays a crucial role in the regulation of cardiovascular homeostasis through its type 1 (AT1) and type 2 (AT2) receptors. Ang II contributes to cardiovascular diseases such as hypertension and atherosclerosis via AT1R activation. Ang II increases blood pressure through Gq-mediated activation of phospholipase C, resulting in phosphoinositide (PI) hydrolysis and increased intracellular calcium levels. Through the AT2R, Ang II counteracts the vasoconstrictor action of AT1R and thereby induces vasodilation, sodium excretion, and reduction of blood pressure. Moreover, AT1R promotes cell proliferation, whereas AT2R inhibits proliferation and stimulates cell differentiation. The AT2R is highly expressed during fetal development, however it is scarcely present in adult tissues and is induced in pathological conditions. Generally, the AT1R mediates many actions of Ang II, while the AT2R is involved in the regulation of blood pressure and renal function.