Human red blood cells inhibit endothelium-derived relaxing factor (EDRF) activity.

We have used a bioassay-cascade system to investigate the inhibitory effects of human red blood cells on EDRF activity. The vascular smooth muscle relaxant effect of EDRF released from an endothelium-intact pig coronary artery by the calcium ionophore A23187 was inhibited by washed red cells. This inhibition of EDRF activity by red cells was similar to that expected from their haemoglobin content. This study provides further evidence that in vivo EDRF acts as a local autocoid.