Possible role of endothelium in the vasodilator response of rat thoracic aorta to platelet activating factor (PAF).

As the endothelium has an important role in the vasodilating effect of acetylcholine, we investigated the possible role of the endothelium in the vasodilating effect of platelet activating factor (PAF). Experiments were done on spirally cut rat thoracic aorta either containing or denuded of endothelial cells. It was demonstrated that relaxation by PAF and acetylcholine of pre-contracted strips required the presence of endothelial cells. The results strongly suggested the possible involvement of endothelium in the vasodilation produced by PAF as well as by ACh.