Receptors on Pulmonary Endothelial Cells

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Abstract
Endothelial cells, situated at the interface of blood and the tissues, are ideally positioned to receive circulating and tissue-derived stimuli and equally to affect underlying cell types of the vascular wall. Endothelial cells and smooth muscle cells show a close morphologic association via myoendothelial junctions and also interact via soluble mediators. We have begun to investigate the stimulus-secretion coupling using agonists that elicit the release of endothelium-derived relaxing factors and have particularly focused on the role of Ca2+. In addition, we have examined the effects of endothelium-derived constrictor substances from both large and small pulmonary vessels. On account of the intimate association between microvessels and the airway wall, we have also examined the effects of endothelium-derived constrictors on tracheal smooth muscle and have shown that conditioned media from pulmonary artery and from pulmonary microvascular endothelial cells constrict both coronary artery rings and tracheal smooth muscle strips. The characteristics of the response are similar to the actions of the 21 amino acid peptide endothelin. Thus, endothelial cells regulate the levels of circulating vasoactive substances via their surface enzymes while, via their surface receptors, they are capable of being stimulated to release substances with effects on vascular tone and airway responses.