Effect of aging on renal blood flow velocity during static exercise

Afsana Momen, Urs Leuenberger, Brian Handly, Lawrence Sinoway

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22 Scopus citations

Abstract

During exercise, activation of the sympathetic nervous system causes reflex renal vasoconstriction. The effects of aging on this reflex are poorly understood. This study evaluated the effects of age on renal vasoconstrictor responses to handgrip. Seven older (65 ± 9 yr) and nine younger (25 ± 2 yr) subjects were studied. Beat-by-beat analyses of changes in renal blood flow velocity (RBV; duplex ultrasound) were performed during two handgrip paradigms. Arterial blood pressure (BP) and heart rate were also measured, and an index of renal vascular resistance (RVR) was calculated (BP/RBV). In protocol 1, fatiguing handgrip [40% of maximal voluntary contraction (MVC)] caused a greater increase in RVR in the older subjects (old 90% ± 15 increase, young 52% ± 4 increase; P = 0.03). During posthandgrip circulatory arrest (isolates muscle metaboreflex), the increases in RVR were only ∼1/2 of the increase seen at end grip. In protocol 2, 15-s bouts of handgrip at graded intensities led to increases in RVR in both subject groups. This effect was not seen until 50% MVC workload (P < 0.05). RVR responses occurred early and were greater in older than in younger subjects at 50% MVC (32 ± 6% vs. 16 ± 5%; P = 0.02) and 70% MVC (39 ± 11% vs. 24 ± 8%; P = 0.02). Static exercise-induced renal vasoconstriction is enhanced with aging. Because the characteristics of this response suggest a predominant role for mechanoreceptor engagement, we hypothesize that mechanoreceptor responses are augmented with aging.

Original languageEnglish (US)
Pages (from-to)H735-H740
JournalAmerican Journal of Physiology - Heart and Circulatory Physiology
Volume287
Issue number2 56-2
DOIs
StatePublished - Aug 2004

All Science Journal Classification (ASJC) codes

  • Physiology
  • Cardiology and Cardiovascular Medicine
  • Physiology (medical)

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