Figure 2.

A phosphorimage showing the regulation of cholera toxin-catalyzed [³²P]-ADP-ribosylation of G_i2 in membranes from main extrapulmonary artery. Membranes (100 mg) from rat extrapulmonary artery were incubated with [³²P]-NAD and thiol-activated cholera toxin (50 mg ml⁻¹) in the absence of ligand, with 0.1 μM ET-1, 1 μM FR139317 or 1 μM BQ-788. Samples were solubilized, immunoprecipitated with antiserum SG1, resolved by SDS–PAGE (10% w v⁻¹ acrylamide) and subjected to autoradiography. This is a representative image of a series of three. In all, densitometrically, there was no difference between the ‘plus ET-1 plus FR139317' band and the ‘control band', neither was there any difference between the ‘plus ET-1 plus BQ-788' band and the ‘plus ET-1' band.