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Contribution of nitric oxide in the contraction‐induced rapid vasodilation in young and older adults
Author(s) -
Casey Darren P.,
Walker Branton G.,
Ranadive Sushant M.,
Taylor Jennifer L.,
Joyner Michael J.
Publication year - 2013
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.27.1_supplement.1136.7
Subject(s) - vasodilation , medicine , brachial artery , forearm , nitric oxide , nitric oxide synthase , vasoconstriction , endocrinology , contraction (grammar) , cardiology , blood pressure , surgery
We tested the hypothesis that reduced nitric oxide (NO) bioavailability contributes to the attenuated peak and total vasodilation following single muscle contractions in older adults. Young (n=8; 25 ± 2 yr) and older (n=9; 67 ± 2 yr) adults performed single forearm contractions at 10, 20 and 40% of maximum during saline infusion (control) and NO synthase (NOS) inhibition via L‐NMMA. Brachial artery diameter and velocities were measured using Doppler ultrasound and forearm vascular conductance (FVC) was calculated from blood flow (ml/min) and blood pressure (mmHg). Peak and total vasodilator responses (ΔFVC from baseline) were attenuated in older adults at all intensities (P < 0.05). NOS inhibition reduced the peak ΔFVC at 10% (95 ± 13 vs. 59 ± 10), 20% (134 ± 11 vs. 90 ± 12) and 40% (222 ± 30 vs. 143 ± 24) in young subjects (P < 0.05 for all) and in older adults at 10% (61 ± 5 vs. 48 ± 7, P < 0.05) and 20% (90 ± 8 vs. 70 ± 8, P < 0.05), but not 40% (129 ± 13 vs. 105 ± 11, P = 0.12). The relative (%) reduction in peak ΔFVC due to NOS inhibition was greater in young vs. older adults at 20% (−36 ± 5 vs. −22 ± 5%, P < 0.05) and 40% (−35 ± 7 vs. −17 ± 7%, P < 0.05). The reduction in the total vasodilator response (area under the curve) with NOS inhibition was also greater in young vs. older adults at 20 and 40%. Our data suggest that contraction‐induced rapid vasodilation is mediated in part by NO; however, it appears the NO contribution in the response is greater in young adults.