Low-dose aspirin inhibits platelet-induced contraction of the human isolated coronary artery. A role for additional 5-hydroxytryptamine receptor antagonism against coronary vasospasm?

The beneficial effect of low-dose aspirin in the prevention of coronary vasospasm is well documented. In this study, we investigated the contractile effect of human washed platelets on the human isolated coronary artery. We concentrated on the effect of low-dose aspirin (40 mg/d) taken by the platelet donor and on the efficacy of thromboxane A2 (TXA2) and 5-hydroxytryptamine (5-HT) receptor antagonists. Human coronary artery segments were suspended in an organ bath set-up for isometric tension measurement. Platelets (10(9) to 3 x 10(10)/L) elicited concentration-dependent contractile responses of the coronary artery segments, reaching 28.4 +/- 7.1% of contractions induced by 100 mmol/L K+. The contractile response tended to be decreased in vessel segments with histological signs of early atherosclerosis. Contraction was significantly attenuated after pretreatment of the vessel segments with ketanserin (5-HT2 receptor antagonist, 1 mumol/L) or SQ30741 (TXA2 receptor antagonist, 0.01 mumol/L), reaching 8.8 +/- 2.3% and 3.2 +/- 2.2% of contraction to 100 mmol/L K+, respectively. Platelets obtained from the same platelet donors after they had taken aspirin (40 mg/d for 7 to 13 days) caused significantly lower contractile responses ...Continue Reading