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Heterogeneous Vasodilator Pathways Underlying Flow Mediated Dilation are Preserved in Healthy Aging

Blocking nitric oxide (NO) and prostaglandin (PG) formation does not uniformly reduce radial artery (RA) flow mediated dilation (FMD) in young adults. We hypothesized that aging would alter these pathways such that blocking NO and PG would reduce RA FMD in older adults (n = 10 (5 men), 65±3 y). RA FMD was measured after brachial artery infusions of saline, N(G)‐ monomethyl‐L‐arginine (L‐NMMA), and ketorolac (KETO) + L‐NMMA. Data were compared to published data in young adults (n = 16 (8 men), 28±5 y). No sex differences were observed in either age group. L‐NMMA reduced FMD in older adults (8.9±3.6 to 5.9±3.7%) although this was not statistically significant (p = 0.08) and did not differ (p = 0.74) from the reduction observed in young adults (10.0±3.8 to 7.6±4.7%; p = 0.03). Shear stimulus normalization abolished the effect of L‐NMMA in both groups. No main or interaction effects of blocking PG on FMD were observed in young or older adults (p >; 0.11). Heterogeneity was observed in dilatory responses to blockade in older adults. L‐NMMA reduced (n = 6; range = 36–123% decrease) or augmented FMD (n = 4; range = 0.4–122% increase). After PG blockade, reduced (48–103% decrease) and augmented (72–118% increase) FMD responses were observed. Contrary to our hypothesis, NO is not obligatory for RA FMD in older adults. Similar to young adults, redundant vasodilatory phenotypes exist in healthy, older humans. Funded by a HH Open Competition Grant