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

A cDNA encoding porcine aortic smooth muscle angiotensin II (AII) rece ptor has been isolated using the homology screening approach and seque nced. Specific binding of [I-125]AII was found in COS-7 cells transfec ted 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 bi nding. COS-7 cells transfected with the cDNA responded to All by only a small increase in the concentration of intracellular free Ca2+. Howe ver, electrophysiological study of the receptor expressed in Xenopus l aevis oocytes provided strong evidence that it could functionally coup le to a second messenger system leading to the mobilization of intrace llular stores of Ca2+. Northern blot analysis in cultured porcine aort ic smooth muscle cells demonstrated that the expression of this gene v aries with the culture media. These results indicate that the cDNA enc odes the functional and regulated AT1 subtype of AII receptors.