Participation of NO in the Vasodilatory Action of Isoespintanol

BACKGROUND: Accumulating evidence suggests that natural compounds and specifically monoterpenes exert a vasodilator action. OBJECTIVE: Our aim was to investigate the vascular effects of isoespintanol (2-isopropil-3,6-dimetoxi-5-metilfenol, ISO) monoterpene isolated from the leaves of Oxandra cf xylopioides. METHODS: Thoracic aortic rings isolated from Wistar rats were contracted with potassium chloride 80 mM and then relaxed by exposure to Ca2+-free solution in absence and in presence of isoespintanol 0.6 g/ml. The force/tissue ratio (F/W) and the time to obtain 50% of relaxation (T-50) were used to assess the maximal contractile response and the relaxation, respectively. To examine the participation of nitric oxide additional experiments were performed under inhibition of nitric oxide synthase with L-NAME (L-NG-Nitroarginine methyl ester). RESULTS: Isoespintanol significantly decreased the F/W ratio (257 ± 19 vs. 360 ± 18) and did not change T-50. In presence of L-NAME the effects of isoespintanol on contractile response was abolished. CONCLUSIONS: These results demonstrate that isoespintanol exerts a vasodilator effect through NO-dependent pathways and suggest that an inhibition of calcium influx could be the involved mechanism.