Coronary artery constriction is enhanced with nicotine and propranolol, particularly after endothelial damage

Coronary artery ring preparations from sheep were used for in vitro assessment of isometric tension after stimulation with adrenaline (NA), serotonin (5-HT) and nicotine (NC). From concentration-response curves the following observations were made on potency of agonist: 5-HT greater than NC greater than NA and efficacy: 5-HT = NC greater than NA. Removal of the intima increased sensitivity to stimulation with NA and 5-HT (lower EC50 values) and augmented the maximal response. Preincubation of the vessels with NC and propranolol (PR) resulted in a leftward shift of the concentration-response curves to NA and 5-HT. Sensitivity and maximal response to NA and 5-HT were further enhanced by endothelial removal and pretreatment with NC and PR. It can be concluded that vasoconstriction to NA and 5-HT is enhanced by nicotine (smoking) and administration of beta-blockers (propranolol), particularly in coronary arteries with endothelial damage.