Quantification of the potencies of EDRF-releasers from isolated rabbit aortic strips

We have compared several known releasers of endothelium-derived relaxing factor (EDRF)(13) in respect to their potencies to generate EDRF by endothelium of rabbit aortic strips (RbA) superfused with Krebs' buffer. The vasorelaxation by EDRF which is equivalent to 10 pmoles of GTN was evoked by 0.7 pmoles of substance P(SP), 50 pmoles of acetylcholine (Ach), 521 pmoles of calcium ionophore A 23187, 2720 pmoles of ADP. Threshold potencies of these agonists are inversely proportional to the maximum amount of EDRF released. Phospholipase C (PLC) from Clostridium perfringens at a dose of 0.1 U caused the relaxation of a similar magnitude. Phospholipase A2 (1 U), thrombin (1 U), bradykinin (30 nmoles) and serotonin (10 pmoles) did not release EDRF. It is concluded that endothelial cells of RbA differ from endothelial cells of other species in their susceptibility to release EDRF in response to various agonists.