RESUMEN
INTRODUCTION: Sympathetic and Renin-Angiotensin-Aldosterone systems play crucial roles in blood pressure response to increased salt intake. This study investigated the effects of angiotensin receptor blocker (ARB) and sympathetic excitation on the responses of blood pressure (BP) and peripheral vascular resistance (PVR) in salt loaded normotensive (NT) and hypertensive (HT) Nigerian subjects. METHODS: 16 NT and 14 HT participants, that were age-matched [39.9 ± 1.3 vs 44.1±2.1yrs (P= 0.10)], underwent 5 days each of oral administration of 200mmol NaCl, and 200mmol NaCl + 50mg Losartan, preceded by a baseline control condition. BP and PVR responses to 30% Maximum Voluntary Contraction (MVC) of handgrip (HG) for one minute were determined at baseline, after salt load and after salt + Losartan. Data were presented as Mean ± SEM, and analyzed with two-way ANOVA and paired t-test, with P<0.05 accepted as significant. RESULTS: BP and PVR were significantly increased by HG at baseline, after salt load and after salt + Losartan in NT and HT. Salt load augmented the HG-induced SBP (P=0.04) and MABP responses (P=0.02) in HT. While Losartan attenuated the HG- induced Systolic Blood Pressure (SBP) SBP response (P=0.007) and DBP response (P=0.003) in HT and NT respectively after salt + Losartan. HG-induced PVR response was significantly accentuated after salt load in HT (P=0.005), but it was not significant in NT (P=0.38). CONCLUSION: The implication of our finding is that angiotensin II receptor blockade possibly attenuates salt-induced sympathetic nerve excitation in black hypertensive patients.
Asunto(s)
Bloqueadores del Receptor Tipo 1 de Angiotensina II/administración & dosificación , Hipertensión/tratamiento farmacológico , Losartán/administración & dosificación , Natriuresis/efectos de los fármacos , Adulto , Bloqueadores del Receptor Tipo 1 de Angiotensina II/farmacología , Antihipertensivos/administración & dosificación , Antihipertensivos/farmacología , Presión Sanguínea/efectos de los fármacos , Estudios de Casos y Controles , Femenino , Fuerza de la Mano , Humanos , Losartán/farmacología , Masculino , Persona de Mediana Edad , Nigeria , Sistema Renina-Angiotensina/efectos de los fármacos , Cloruro de Sodio DietéticoRESUMEN
Regional heterogeneity exists in reactivity of different vascular beds to vasoactive substances. Experiments were designed to determine if there are differences between thoracic and abdominal aorta response to acetylcholine-induced relaxation. Ten male Sprague-Dawley rats with a weighing between 200g-250g were used. The aorta was isolated and 3mm aortic rings were cut and suspended in organ baths containing physiological salt saline (PSS). Contractile and relaxation responses to noradrenaline (NA) and ACh, in the presence or absence of L-NNA and high K+ concentration were studied. Contractile response to NA was similar along the aorta. At the higher doses, ACh elicited a greater (p < 0.05) relaxation in the abdominal aorta when compared with the thoracic aorta. However, inhibition of eNOS was more effective (p<0.05) in preventing ACh-induced relaxation in the thoracic aorta when compared with the abdominal aorta. Conversely, inhibition of endothelial hyperpolarizing factor (EDHF) by high K+ concentration blocked ACh-induced relaxation to a greater extent in the abdominal aorta (p<0.05) when compared with the thoracic aorta. ACh-induced relaxation differs in the thoracic and abdominal aorta. Differences in the EDHF activity along the aorta underlie the differential response of the thoracic and abdominal aorta to ACh-induced relaxation.