EDRF generation and release from perfused bovine pulmonary artery and vein

A bioassay cascade superfusion procedure was utilized to study the release and effects of endothelium-derived relaxing factor (EDRF) from isolated bovine pulmonary artery and vein. Three precontracted, endothelium-denuded strips of pulmonary artery or vein mounted in series served as the detector of EDRF. Perfusion of artery with acetylcholine, bradykinin or A23187, in the presence of indomethacin, caused the release of EDRF (t1/2 = 3-5 s) which relaxed superfused strips of both artery and vein. Similarly, perfusion of vein with bradykinin or A23187, but not acetylcholine, caused the release of EDRF (t1/2 = 3-5 s) which relaxed superfused strips of both vein and artery. EDRF-elicited vascular smooth muscle relaxation was associated with cyclic GMP accumulation in the superfused strips. EDRF activity was increased and its duration prolonged by superoxide dismutase or low oxygen tension, whereas oxyhemoglobin and methylene blue were markedly inhibitory. The similar patterns of release, instability, and properties of EDRF from intact artery and vein suggest that arterial and venous EDRF are closely similar.