['To determine whether or not low molecular G-proteins are involved in the endothelium-dependent relaxations to bradykinin.', 'The effects of botulinum ADP-ribosyltranferase C3 were studied in porcine coronary arteries and endothelial cells.', "Incubation of membrane fractions isolated from endothelial cells with the enzyme and 32P-NAD resulted in the ribosylation of the proteins with molecular weight of 24-25 kDa. Radio labelling of these proteins was suppressed in the presence of guanosine 5'-O-(3-thiotriphosphate) (GTP-gammaS), a hydrolysis-resistant analog of GTP. In the isolated arteries, ADP-ribosyltransferase C3 attenuated the relaxations to bradykinin during contractions with prostaglandin F2alpha in the presence of tween 80 (non ionic detergent), but not in the absence of tween 80."] Do low molecular weight G-proteins of rho-family mediate relaxations to bradykinin in porcine coronary arteries?