Biochemical characterization of two angiotensin II receptor subtypes in the rat.

Two angiotensin II receptor subtypes, A and B, have been described by means of specific and selective ligands (Biochem Biophys Res Commun 1989; 163:284-91). The present report describes the binding characteristics and the distribution of these subtypes in various rat tissues. Adrenal and uterus expressed both subtypes but in different proportions. Subtype B predominated in the adrenal glomerulosa (60%), whereas there was a greater proportion of subtype A in the medulla (70%). In uterus, subtype B was preferentially expressed (70%), and there was no difference in receptor distribution between muscle layers and serosa. Liver, kidney, and cultured aortic smooth muscle cells expressed only subtype B. In all of the tissues tested, the Ki values of various competing ligands were similar for each subtype expressed. It is proposed that subtype B is the vascular receptor. The function of subtype A, however, is still to be determined.