β‐ADRENOCEPTORS ON ENDOTHELIAL CELLS DO NOT INFLUENCE RELEASE OF RELAXING FACTOR IN DOG CORONARY ARTERIES

Abstract

1. The aim of this study was to determine if stimulation of a β‐adrenoceptor on endothelial cells could release an endothelium‐derived relaxing factor (EDRF) similar to that released by acetylcholine. 2. In dog coronary rings preconstricted with PGF2α or serotonin, removal of the endothelium did not alter the relaxant responses to isoprenaline. However, in rings preconstricted with the thromboxane‐mimetic U46619, removal of the endothelium enhanced the response to isoprenaline. 3. The vasorelaxant responses to isoprenaline in endothelium‐denuded rings were inhibited in a concentration‐dependent manner by the specific β1‐adrenoceptor antagonist CGP‐20712A (3–100 nmol/l), but were not altered ..