The cardiopulmonary reflexes of spontaneously hypertensive rats are normalized after regression of left ventricular hypertrophy and hypertension

Cardiopulmonary reflexes are activated via changes in cardiac filling pressure (volume-sensitive reflex) and chemical stimulation (chemosensitive reflex). The sensitivity of the cardiopulmonary reflexes to these stimuli is impaired in the spontaneously hypertensive rat (SHR) and other models of hypertension and is thought to be associated with cardiac hypertrophy. The present study investigated whether the sensitivity of the cardiopulmonary reflexes in SHR is restored when cardiac hypertrophy and hypertension are reduced by enalapril treatment. Untreated SHR and WKY rats were fed a normal diet. Another groups of rats were treated with enalapril (10 mg kg-1 day-1, mixed in the diet; SHRE or WKYE) for one month. After treatment, the volume-sensitive reflex was evaluated in each group by determining the decrease in magnitude of the efferent renal sympathetic nerve activity (RSNA) produced by acute isotonic saline volume expansion. Chemoreflex sensitivity was evaluated by examining the bradycardia response elicited by phenyldiguanide administration. Cardiac hypertrophy was determined from the left ventricular/body weight (LV/BW) ratio. Volume expansion produced an attenuated renal sympathoinhibitory response in SHR as compared to WKY rats. As compared to the levels observed in normotensive WKY rats, however, enalapril treatment restored the volume expansion-induced decrease in RSNA in SHRE. SHR with established hypertension had a higher LV/BW ratio (45%) as compared to normotensive WKY rats. With enalapril treatment, the LV/BW ratio was reduced to 19% in SHRE. Finally, the reflex-induced bradycardia response produced by phenyldiguanide was significantly attenuated in SHR compared to WKY rats. Unlike the effects on the volume reflex, the sensitivity of the cardiac chemosensitive reflex to phenyldiguanide was not restored by enalapril treatment in SHRE. Taken together, these results indicate that the impairment of the volume-sensitive, but not the chemosensitive, reflex can be restored by treatment of SHR with enalapril. It is possible that by augmenting the gain of the volume-sensitive reflex control of RSNA, enalapril contributed to the reversal of cardiac hypertrophy and normalization of arterial blood pressure in SHR

Estudo químico e da atividade biológica cardiovascular do óleo essencial de folhas de Alpinia zerumbet (Pers.) B.L.Burtt & R.M.Sm. em ratos Phytochemistry and cardiovascular biological activity of the essential oil from leaves of Alpinia zerumbet (Pers.) B.L. Burtt & R.M.Sm. in rats

A espécie vegetal Alpinia zerumbet (Pers.) B.L.Burtt & R.M. Sm. é popularmente empregada para o tratamento de diversas enfermidades, entre elas a hipertensão. Avaliar a composição química, a atividade antihipertensiva e ação na hipertrofia cardíaca do óleo essencial das folhas de Alpinia zerumbet (OEAZ) em ratos foram os objetivos deste estudo. O OEAZ, obtido por hidrodestilação em aparelho Clevenger, teve sua composição química analisada em cromatografia gasosa acoplada à espectrometria de massas (CG-EM). Foram identificados 14 constituintes, sendo terpinen-4-ol (37,45%) o majoritário, seguido pelos óxido de cariofileno (7,56%), trans-hidrato de sabineno (6,61%) e 1,8-cineol (4,02%). A avaliação cardiovascular foi feita após o tratamento crônico de ratos espontaneamente hipertensos (SHR) e seus respectivos controles, ratos Wistar-Kyoto (WKY). Os dados hemodinâmicos revelaram redução da pressão arterial média (PAM) no grupo tratado (SHRP: 160 ± 7 mm Hg; p<0,01) em relação ao não tratado (SHR: 180 ± 5 mm Hg). A relação entre peso do ventrículo esquerdo e peso corporal (VE/PC) do SHRP (2,50 ± 0,03 mg g-1; p<0,01) mostrou-se inferior ao SHR (2,61 ± 0,01 mg g-1), confirmando a redução da hipertrofia cardíaca (HC). Os dados de PAM e VE/PC dos animais SHRP foram estatisticamente diferentes quando comparados com os ratos controle (WKY: 116 ± 2 mm Hg e WKYP: 119 ± 4 mm Hg; p<0,05; WKY: 2,15 ± 0,04 mg g-1 e WKYP: 2,17 ± 0,04 mg g-1 ; p<0,01), indicando não ter havido normalização dos mesmos. Conclui-se que o tratamento crônico com OEAZ foi capaz de determinar redução, mas não a normalização, da PAM e da HC de ratos SHR, provavelmente pela presença dos componentes terpinen-4-ol e 1,8-cineol. Estudos com doses maiores ou período de tratamento superior são necessários para avaliar a possibilidade de o OEAZ normalizar os parâmetros analisados (PAM e HC).<br>Alpinia zerumbet (Pers.) B.L. Burtt & R.M.Sm. is traditionally employed to treat several diseases such as hypertension. The aim of this study was to evaluate the chemical composition, the anti-hypertensive activity and the capacity to reduce cardiac hypertrophy of the essential oil of A. zerumbet leaves (EOAZ) in rats. EOAZ was obtained through hydrodistillation in Clevenger apparatus and its chemical composition was analyzed by gas chromatography-mass spectrometry (GC-MS). Several constituents (14) were identified, terpen-4-ol (37.45%) being the major component, followed by caryophyllene oxide (7.56%), trans-sabinene hydrate (6.61%) and 1,8-cineol (4.02%). The cardiovascular effect was investigated after chronic treatment with spontaneously hypertensive rats (SHR) and their respective controls, Wistar-Kyoto rats (WKY). The treated group showed a lower mean arterial pressure (MAP) (SHRP: 160 ± 7 mm Hg; p<0.01) than the untreated group (SHR: 180 ± 5 mm Hg). The ratio of left ventricle-to-body weight (LV/BW) for SHRP was lower (2.504 ± 0.03 mg g-1; p<0.01) than that for SHR (2.162 ± 0.01 mg g-1), confirming the cardiac hypertrophy (CH) reduction. There were significant differences in MAP and CH between SHRP animals and control rats (WKY: 116 ± 2 mm Hg and WKYP: 119 ± 4 mm Hg; p<0.05. WKY: 2.152 ± 0.04 mg g-1 and WKYP: 2.168 ± 0.04 mg g-1; p<0.01), indicating that these values were not normalized. Those data showed that the chronic treatment with EOAZ reduces MAP and CH in SHR probably due to the presence of the compounds terpinen-4-ol and 1,8-cineol. Studies with higher doses or longer treatment periods are necessary to evaluate whether EOAZ can reduce the analyzed parameters (MAP and CH) to normal values