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1 Department of Integrative Physiology, University of Colorado, Boulder, CO, USA
2 Department of Integrative Physiology, University of Colorado, Boulder, CO, USA; Divisions of Cardiology and Geriatric Medicine Department of Medicine, University of Colorado Health Sciences Center, Denver, CO, USA
* To whom correspondence should be addressed. E-mail: kmonahan{at}psu.edu.
Cardiovagal baroreflex sensitivity (BRS) declines with advancing age in healthy men. We tested the hypothesis that oxidative stress contributes mechanistically to this age-associated reduction. Eight young (23±1 years old, mean±SE) and 7 older (63±3) healthy men were studied. Cardiovagal BRS was assessed using the modified Oxford technique (bolus infusion of 50-100
µg sodium nitroprusside followed 60 s later by a 100-150 µg bolus of phenylephrine hydrochloride) in triplicate at baseline and during acute intravenous ascorbic acid infusion. At baseline, cardiovagal BRS (slope of the linear portion of the R-R interval-systolic blood pressure relation during pharmacological changes in arterial blood pressure) was 56% lower (P<0.01) in
older (8.3±1.6 ms/mmHg) compared with young (19.0±3.1 ms/mmHg) men. Ascorbic acid infusion increased plasma concentrations similarly in young (62±9 vs. 1249±72 µmol/L for
baseline and during ascorbic acid; P<0.05) and older men (62±4 vs. 1022±55 µmol/L; P<0.05)
without affecting baseline blood pressure, heart rate, carotid artery compliance, or the magnitude of change in systolic blood pressure in response to bolus sodium nitroprusside and phenylephrine hydrochloride infusion. Ascorbic acid (vitamin C) infusion increased cardiovagal BRS in older (
58±16%; P<0.01), but not younger (-4±4%) men. These data provide experimental support for the concept that oxidative stress contributes mechanistically to age-associated reductions in
cardiovagal BRS in healthy men.
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