G-PROTEINS IN AORTIC ENDOTHELIAL-CELLS AND BRADYKININ-INDUCED FORMATION OF NITRIC-OXIDE

In bovine aortic endothelial cells (BAEC), pertussis toxin (PTx) ADP-ribosylated two major substrates with apparent molecular masses of 40 and 41 kDa, whereas cholera toxin (CTx) ADP-ribosylated two other substrates of 44 and 50 kDa. [alpha-P-32]GTP bound to three bands in the 22-27 kDa range. Immunoblot analysis revealed the simultaneous presence of G(alphai1), G(alphai2), G(alphai3), G(alphaq) or G(alpha11) and of different forms of G(alphas) but did not detect significant levels of G(alpha0). Bradykinin caused a 9-fold increase in intracellular cyclic-GMP level in BAEC (measured as an index of NO production). Preincubation of BAEC with CTx, but not with PTx, inhibited bradykinin-dependent production of cyclic GMP. These results show that G(alphas, G(alphaq or alpha11), G(i) and small GTP-binding proteins are present in BAE-C and suggest that a CTx-sensitive G-protein (possibly either small G-protein, G(alphaq) or G(alpha11)) could be associated with the bradykinin-mediated NO formation.