Calcium antagonism and the vasorelaxation of the rat aorta induced by rotundifolone

the vasorelaxing activity of rotundifolone (rot), a major constituent (63.5%) of the essential oil of mentha x villosa, was tested in male wistar rats (300-350 g). in isolated rat aortic rings, increasing rot concentrations (0.3, 1, 10, 100, 300, and 500 μg/ml) inhibited the contractile effects of 1 μm phenylephrine and of 80 or 30 mm kcl (ic50 values, reported as means ± sem = 184 ± 6, 185 ± 3 and 188 ± 19 μg/ml, n = 6, respectively). in aortic rings pre-contracted with 1 μm phenylephrine, the smooth muscle-relaxant activity of rot was inhibited by removal of the vascular endothelium (ic50 value = 235 ± 7 μg/ml, n = 6). furthermore, rot inhibited (pd2 = 6.04, n = 6) the cacl2-induced contraction in depolarizing medium in a concentration-dependent manner. in ca2+-free solution, rot inhibited 1 μm phenylephrine-induced contraction in a concentration-dependent manner and did not modify the phasic contractile response evoked by caffeine (20 mm). in conclusion, in the present study we have shown that rot produces an endothelium-independent vasorelaxing effect in the rat aorta. the results further indicated that in the rat aorta rot is able to induce vasorelaxation, at least in part, by inhibiting both: a) voltage-dependent ca2 channels, and b) intracellular ca2+ release selectively due to inositol 1,4,5-triphosphate activation. additional studies are required to elucidate the mechanisms underlying rot-induced relaxation.