[1] They are important in the renin–angiotensin system: they are responsible for the signal transduction of the vasoconstricting stimulus of the main effector hormone, angiotensin II.
The AT1 subtype is found in the heart, blood vessels, kidney, adrenal cortex, lung and circumventricular organs of brain, basal ganglia, brainstem[4] and mediates the vasoconstrictor effects.
[2] 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.
Effects mediated by the AT2 receptor are suggested to include inhibition of cell growth, fetal tissue development, modulation of extracellular matrix, neuronal regeneration, apoptosis, cellular differentiation, and maybe vasodilation and left ventricular hypertrophy.
In the mouse is found in the adrenal gland, amygdaloid nuclei and, in small numbers, in the paraventricular nucleus of the hypothalamus and the locus coeruleus.