Efeitos do extrato aquoso da murta (Blepharocalyx salicifolius) e possíveis mecanismos de ação envolvidos sobre os parâmetros hemodinâmicos de ratos

Abstract

Hypertension is finds as a multifactorial clinical condition characterized by high and sustained levels of blood pressure. Disease progression are intimately linked with structural and functional cardiac and vascular changes, promoting some damage in target organs such as the kidneys, brain, in addition to metabolic changes that produce a significant increase in the risk of cardiovascular diseases. According to the Brazilian Society of Cardiology, hypertension has a high prevalence and low control rates, making it one of the most important public health problems in Brazil. The use of medicinal plants for therapeutic purposes is quite old and often its use is completely empirical, no scientific study that basement this practice. Blepharocalyx salicifolius, known as Murta, has several therapeutic utilities based on popular knowledge, including use as digestive, antibacterial, antispasmodic and antihypertensive, among others. The present study evaluated the hypotensive effect of aqueous extract of B. salicifolius in normotensive rats and analyzed with L-NAME, the losartan and hexamethonium, which would be its possible mechanism of action. The evaluation of the hemodynamic effects was perform in normotensive Wistar rats, anesthetized with urethane (1.4 mg / kg i.p.) and cannulated in the carotid artery (for verification of SBP, DBP and HR) and the jugular vein (for administration of the extract and drugs). The first protocol was performed to verify the effect of the extract on the hemodynamic parameters using a dose increasing curve of the extract (10, 25, 50, 75 and 100 mg/kg) intravenously individually (each group containing six animals). The administration of the aqueous extract was after 30 minutes of stabilization in the equipment, and they remained for 60 min. The second protocol was to evaluate some of the possible mechanisms involved in the hypotensive response. Were used: an inhibitor of nitric oxide synthase - L-NAME (L-NG-L-nitroarginine methyl ester) (30 mg / kg); AT1 receptor antagonist - losartan (10 mg / kg), and a ganglionic blocker - hexamethonium (20mg/kg). Drug administration was performed after stabilization, performing a new stabilization for the administration of the extract and records kept for 60 min. The aqueous extract of B. salicifolius proved a potent hypotensive effect, reducing blood pressure in a dose-independent way since the declines were similar regardless of the dose used, and without effect on heart rate. In evaluation of the possible mechanism of action it was observed, when the AT1 receptor were blockade and the extract was administrated, that there was no change in blood pressure caused by losartan as after ganglionic blockage. When hypertension was induced by L-NAME, the extract caused arterial pressure low, suggesting that the nitric oxide pathway could not be involved. These results show for the first time that the hypotensive effect of acute administration of Blepharocalyx salicifolius aqueous extract may be by blockade of angiotensin II type 1 receptors and the possible reduction in sympathetic autonomic response.