Aspirin and COX-2 Inhibitor Nimesulide Potentiate Adrenergic Contractions of Human Gastroepiploic Artery

Background The aim of the present study was to evaluate the intervention of COX-1- and COX-2-derived prostaglandins in the responses of human gastroepiploic artery to sympathetic stimulation and norepinephrine. Methods Rings of human gastroepiploic artery were obtained from 45 patients (26 men and 19 women) undergoing gastrectomy. The rings were suspended in organ baths for isometric recording of tension. We studied the responses to electrical field stimulation, norepinephrine, and acetylcholine, in the absence and presence of COX-1 or COX-2 inhibition. Results The COX-1 and COX-2 inhibitor aspirin at high concentrations (10−6 to 10−5 mol/L) and the COX-2 inhibitor nimesulide (10−6 mol/L) potentiated the contractile responses of the arterial rings to sympathetic neurogenic stimulation and norepinephrine. In contrast, lower concentrations of aspirin (10−8 to 10−7 mol/L) or the COX-1 inhibitor SC-560 (3 ×10−8 mol/L) did not affect these responses. The vascular relaxation induced by acetylcholine was not affected by COX-1 and COX-2 inhibition. Conclusions The results provide functional evidence that vasodilator prostaglandins are active components of the response of human gastroepiploic artery to neurogenic stimulation and norepinephrine. Aspirin at high concentrations and the COX-2 selective inhibitor nimesulide potentiated the contractile response of gastroepiploic artery to adrenergic stimulation by inhibiting COX-2-derived PGI2. Aspirin at low concentrations and the COX-1 selective inhibitor SC-560 did not modify the contractile responses, possibly due to minor importance of vasoconstrictor prostaglandins (TXA2) as active components of the response of gastroepiploic artery to adrenergic stimulation.