Angiotensin receptor blockade with Losartan attenuates pressor response to handgrip contraction and enhances natriuresis in salt loaded hypertensive subjects: a quasi-experimental study among Nigerian adults

Abstract

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 200 mmol NaCl, and 200 mmol NaCl + 50 mg 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 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.

Keywords

• handgrip contraction
• sodium excretion
• vascular resistance
• losartan
• hypertensive nigerians
• maximum voluntary contraction