MOLECULAR-CLONING AND CHARACTERIZATION OF THE ANGIOTENSIN RECEPTOR SUBTYPE IN PORCINE AORTIC SMOOTH-MUSCLE

A cDNA encoding porcine aortic smooth muscle angiotensin II (AII) receptor has been isolated using the homology screening approach and sequenced. Specific binding of [I-125]AII was found in COS-7 cells transfected with the cDNA (K(d) = 0.37 nM, B(max) = 1 approximately 3 X 10(4)/cell) and was displaced with unlabeled AII-related peptides and DUP753 in the order of [Sar1,Ile8]AII = AII > des-Asp1-[Ile8]AII = DUP753 > angiotensin I = angiotensin III. EXP655 had no effect on [I-125]AII binding. COS-7 cells transfected with the cDNA responded to All by only a small increase in the concentration of intracellular free Ca2+. However, electrophysiological study of the receptor expressed in Xenopus laevis oocytes provided strong evidence that it could functionally couple to a second messenger system leading to the mobilization of intracellular stores of Ca2+. Northern blot analysis in cultured porcine aortic smooth muscle cells demonstrated that the expression of this gene varies with the culture media. These results indicate that the cDNA encodes the functional and regulated AT1 subtype of AII receptors.