ANGIOTENSIN-II BINDING-ACTIVITY IN CULTURED PORCINE ARTERIAL ENDOTHELIAL-CELLS

Angiotensin II (A II) binding activity was detected in the particulate fraction (100,000 g, 60 min precipitate) of cultured porcine aortic e ndothelial cells. Scatchard analysis of the binding activity indicated a single class of binding sites with a dissociation constant (K-d) of 1.1 nM and a total binding capacity B-max of 125 fmol/mg protein. The binding of [I-125]A II was inhibited by excess unlabelled A II, A II analogues ([Sar(1), Ile(8)]A II and [Sar(1), Ala(8)]A II), A I (angiot ensin I) and A III (angiotensin III), but not by bradykinin. Type spec ific A II receptor antagonists, losartan (type 1 angiotensin II recept or) and PD123319 (type 2 angiotensin II receptor), did not inhibit the binding. These results suggest that the A II specific binding protein (s) or receptor(s) is present in arterial endothelial cells, and that it is different from typical type 1 and type 2 angiotensin If receptor s.