Preliminary biochemical characterization of two angiotensin II receptor subtypes

Two angiotensin II receptor subtypes (A and B) are described from rat and human tissues. They have been characterised using specific peptidic and non-peptidic ligands with affinities differing by 1000 fold or more. These subtypes are present in adrenal glomerulosa of both species. Human uterus contains only subtype A, whereas both subtypes are found in rat uterus. Vascular smooth muscle cells in culture express only subtype B. Dithio-threitol totally inhibits binding to subtype B, but enhances the affinity to subtype A. There is a good correlation between the affinities of the selected agonists and antagonists for the two subtypes in the various tissues tested which is a usual requirement for receptor classification.