Vascular smooth muscle sensitivity to endothelium-derived relaxing factor is different in different arteries.

1. The relaxation responses of pre-constricted pig coronary artery (PCA) and rabbit aorta (RA) without endothelium, to endothelium-derived relaxing factor (EDRF) released from either a PCA or RA with intact endothelium have been studied by use of a bioassay cascade system. Effects of EDRF have been compared with sodium nitroprusside (NaNP) and 8-bromo-cyclic GMP. 2. The time course of changes in cyclic GMP levels in response to EDRF in PCA and RA have also been studied. 3. EDRF (released from a PCA or RA) caused significantly greater relaxation in the PCA than the RA, whether 5-hydroxytryptamine or high extracellular potassium was used as the constrictor agonist. 4. These differences in sensitivity to EDRF were paralleled by NaNP but not 8-bromo-cyclic GMP. 5. Cyclic GMP levels peaked earlier in the RA (30s) than in the PCA (180s) but the peak levels were significantly greater in the PCA (2.45 fold) than the RA (1.48 fold). 6. These data show that the previously described differences in EDRF activity between different artery types can be explained in part by differences in the responsiveness of the smooth muscle to EDRF.