Effect of angiotensin AT1 receptor blockade on sympathetic responses to handgrip in healthy men

Abstract

BackgroundTo determine whether angiotensin II (ANG II) contributes to the reflex skeletal muscle sympathoexcitation elicited by isometric and isotonic exercise, we tested the hypothesis that angiotensin AT 1 receptor blockade (ARB) would attenuate reflex sympathoneural responses to handgrip (HG) and to post-handgrip ischemia (PHGI).MethodsSeventeen healthy men were studied before and 1 week after random double-blind crossover allocation to oral losartan (100mg daily) and placebo. Heart rate (HR), blood pressure (BP), and muscle sympathetic nerve activity (MSNA) were recorded at rest, and during 2min bouts of isotonic HG at 50% maximum voluntary contraction (MVC) and isometric HG at 30% MVC, performed randomly, each followed by 2min of PHGI.ResultsAt rest, losartan doubled plasma renin (P = 0.01) and ANG II (P = 0.03) concentrations, and lowered BP (P <0.01) yet had no effect on MSNA burst frequency or incidence. HR trended higher (P = 0.060). Losartan's hypotensive effect persisted throughout each exercise bout (P <0.045). MSNA and HR responses to isotonic exercise and postexercise ischemia were not affected by losartan. Isometric exercise and postexercise ischemia increased MSNA on both sessions (all P <0.01). Losartan augmented the HR response (P ≤0.03), and after losartan MSNA burst frequency (P <0.01) and incidence (P <0.04) were significantly higher at all time points, but the magnitude of the MSNA response to isometric exercise and postexercise ischemia was unchanged.ConclusionIn healthy men, short-term ARB does not attenuate reflex sympathoneural responses to HG or PHGI. © 2011 American Journal of Hypertension, Ltd.