The AT1 receptor is the best elucidated angiotensin receptor.
It is activated by angiotensin II. It is coupled to Gq/11 and Gi/o and thus activates phospholipase C and increases the cytosolic Ca2+ level, which itself performs cellular mechanisms, as well as activating protein kinase C It also inhibits adenylate cyclase and activate various tyrosine kinases.
Effects mediated by the AT1 receptor include vasoconstriction, aldosterone synthesis and secretion, increased vasopressin secretion, cardiac hypertrophy, augmentation of peripheral noradrenergic activity, vascular smooth muscle cells proliferation, decreased renal blood flow, renal renin inhibition, renal tubular sodium reuptake, modulation of central sympathetic nervous system activity, cardiac contractility, central osmocontrol and extracellular matrix formation.
AT2 receptors are more plentiful in the fetus and neonate. Effects mediated by the AT2 receptor include inhibition of cell growth, fetal tissue development, modulation of extracellular matrix, neuronal regeneration, apoptosis, cellular differentiation and maybe vasodilation.
AT3 and AT4
Other poorly characterized subtypes include the AT3 and AT4 receptors. The AT4 receptor is activated by the angiotensin II metabolite angiotensin IV, and may play a role in regulation of the CNS extracellular matrix.
^ de Gasparo M, Catt KJ, Inagami T, Wright JW, Unger T (2000). "International union of pharmacology. XXIII. The angiotensin II receptors". Pharmacol. Rev.52 (3): 415–72. PMID 10977869.
^ ab Higuchi S, Ohtsu H, Suzuki H, Shirai H, Frank GD, Eguchi S (2007). "Angiotensin II signal transduction through the AT1 receptor: novel insights into mechanisms and pathophysiology". Clin. Sci.112 (8): 417–28. doi:10.1042/CS20060342. PMID 17346243.
^ Unless else specified in box, then ref is: Senselab
^ Catt KJ, Mendelsohn FA, Millan MA, Aguilera G (1984). "The role of angiotensin II receptors in vascular regulation". J. Cardiovasc. Pharmacol.6 Suppl 4: S575–86. PMID 6083400.