Spasmolytic effect of curcumin on goat ruminal artery is endothelium independent and by activation of sGC

The aim of the present work was to study the mechanism of action of curcumin in vasomotion of a physiologically important artery of ruminant i.e. ruminal artery. ACh and SNP were used to study the role of endothelium in relaxation of this artery. Vasorelaxatation by curcumin was studied in a dose dependent manner, on rings precontracted with 5-hydroxy tryptamine and noradrenalin, in presence and absence of L-NAME, 4AP, ODQ and 4AP + ODQ combination. SNP (1 ηM–100 μM) produced a significant relaxation compared to ACh (0.1–100 μM) on 5-HT (10 μM) and NA (10 μM) induced contraction in endothelium intact rings. Curcumin (10 ηM–100 μM) relaxed the vascular rings in dose dependent manner with maximal relaxation up to 20.94% and 13.81% in 5-HT and NA induced contraction, respectively which was potently blocked by ODQ (10 μM) and combination of 4AP and ODQ (10 μM) but 4AP (10 μM) and L-NAME (100 μM) alone could not block the relaxation and interestingly we observed a slight increase in the tension at higher dose of the agonist (>10 μM). Therefore in goat ruminal artery, curcumin at least in part, act via direct activation of sGC mediated cGMP pathway followed by opening of K+ ion channel. However other mechanisms may not be ruled out.