Impact of aging on conduit artery retrograde and oscillatory shear at rest and during exercise: role of nitric oxide.
Aging has been recently associated with increased retrograde and oscillatory shear in peripheral conduit arteries, a hemodynamic environment that favors a proatherogenic endothelial cell phenotype. We evaluated whether nitric oxide (NO) bioavailability in resistance vessels contributes to age-related differences in shear rate patterns in upstream conduit arteries at rest and during rhythmic muscle contraction. Younger (n=11, age 26 ± 2 years) and older (n=11, age 61 ± 2 years) healthy subjects received intra-arterial saline (control) and the NO synthase inhibitor N(G)-Monomethyl-L-arginine. Brachial artery diameter and velocities were measured via Doppler ultrasound at rest and during a 5-minute bout of rhythmic forearm exercise. At rest, older subjects exhibited greater brachial artery retrograde and oscillatory shear (-13.2 ± 3.0 s(-1) and 0.11 ± .0.02 arbitrary units, respectively) compared with young subjects (-4.8 ± 2.3 s(-1) and 0.04 ± 0.02 arbitrary units, respectively; both P<0.05). NO synthase inhibition in the forearm circulation of young, but not of older, subjects increased retrograde and oscillatory shear (both P<0.05), such that differences between young and old at rest were abolished (both P>0.05). From rest to steady-state exercise, older subjects decreased retrograde and oscillatory shear (both P<0.05) to the extent that no exercise-related differences were found between groups (both P>0.05). Inhibition of NO synthase in the forearm circulation did not affect retrograde and oscillatory shear during exercise in either group (all P>0.05). These data demonstrate for the first time that reduced NO bioavailability in the resistance vessels contributes, in part, to age-related discrepancies in resting shear patterns, thus identifying a potential mechanism for increased risk of atherosclerotic disease in conduit arteries.
Department of Biomedical Sciences, University of Missouri, Columbia, MO 65211, USA. padillaja@missouri.edu
Jaume
J
Padilla
Grant H
GH
Simmons
Paul J
PJ
Fadel
M Harold
MH
Laughlin
Michael J
MJ
Joyner
Darren P
DP
Casey
D000328:Adult; D000367:Age Factors; D000368:Aged; D000375:Aging / Q000502:physiology*; D000704:Analysis of Variance; D001783:Blood Flow Velocity / Q000187:drug effects / Q000502:physiology; D001916:Brachial Artery / Q000000981:diagnostic imaging / Q000187:drug effects / Q000502:physiology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D015444:Exercise / Q000502:physiology*; D006801:Humans; D008875:Middle Aged; D009569:Nitric Oxide / Q000502:physiology*; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors; D012039:Regional Blood Flow / Q000502:physiology; D014463:Ultrasonography; D019323:omega-N-Methylarginine / Q000494:pharmacology
D004791:Enzyme Inhibitors; D019323:omega-N-Methylarginine; D009569:Nitric Oxide; D019001:Nitric Oxide Synthase
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