Nitric Oxide, but not Vasodilating Prostaglandins, Contributes to the Improvement of Exercise Hyperemia via Ascorbic Acid in Healthy Older Adults
Document Type
Article
Publication Date
11-2010
Publication Source
American Journal of Physiology - Heart and Circulatory Physiology
Abstract
Acute ascorbic acid (AA) administration increases muscle blood flow during dynamic exercise in older adults, and this is associated with improved endothelium-dependent vasodilation. We directly tested the hypothesis that increase in muscle blood flow during AA administration is mediated via endothelium-derived vasodilators nitric oxide (NO) and prostaglandins (PGs). In 14 healthy older adults (64 ± 3 yr), we measured forearm blood flow (FBF; Doppler ultrasound) during rhythmic handgrip exercise at 10% maximum voluntary contraction. After 5-min steady-state exercise with saline, AA was infused via brachial artery catheter for 10 min during continued exercise, and this increased FBF ∼25% from 132 ± 16 to 165 ± 20 ml/min (P < 0.05). AA was infused for the remainder of the study. Next, subjects performed a 15-min exercise bout in which AA + saline was infused for 5 min, followed by 5 min of the nitric oxide synthase (NOS) inhibitorNG-monomethyl-L-arginine (L-NMMA) and then 5 min of the cyclooxygenase inhibitor ketorolac (group 1). The order of inhibition was reversed in eight subjects (group 2). In group 1, independent NOS inhibition reduced steady-state FBF by ∼20% (P < 0.05), and subsequent PG inhibition had no impact on FBF (Δ 3 ± 5%). Similarly, in group 2, independent PG inhibition had little effect on FBF (Δ −4 ± 4%), whereas subsequent NO inhibition significantly decreased FBF by ∼20% (P < 0.05). In a subgroup of five subjects, we inhibited NO and PG synthesis before AA administration. In these subjects, there was a minimal nonsignificant improvement in FBF with AA infusion (Δ 7 ± 3%; P = nonsignificant vs. zero). Together, our data indicate that the increase in muscle blood flow during dynamic exercise with acute AA administration in older adults is mediated primarily via an increase in the bioavailability of NO derived from the NOS pathway.
Inclusive pages
H1633-H1641
ISBN/ISSN
0363-6135
Publisher
American Physiological Society
Volume
299
Issue
5
Peer Reviewed
yes
Sponsoring Agency
National Institutes of Health
eCommons Citation
Crecelius, Anne R.; Kirby, Brett S.; Voyles, Wyatt F.; and Dinenno, Frank A., "Nitric Oxide, but not Vasodilating Prostaglandins, Contributes to the Improvement of Exercise Hyperemia via Ascorbic Acid in Healthy Older Adults" (2010). Health and Sport Science Faculty Publications. 24.
https://ecommons.udayton.edu/hss_fac_pub/24
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Comments
Article is also available through PubMed Central at http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2993219/