Cyclooxygenase (COX) contributes to cutaneous vasodilation and sweating responses; however, the mechanisms underpinning these responses remain unknown. We hypothesized that prostaglandin E1 (PGE1) and E2 (PGE2) (COX-derived vasodilator products) directly mediate cutaneous vasodilation and sweating through nitric oxide synthase (NOS)-dependent mechanisms in young adults. Furthermore, we hypothesized that this response is diminished in older adults, since aging attenuates COX-dependent cutaneous vasodilation and sweating. In 9 young (22 ± 5 yr) and 10 older (61 ± 6 yr) adults, cutaneous vascular conductance (CVC) and sweat rate were evaluated at four intradermal forearm skin sites receiving incremental doses (0.05, 0.5, 5, 50, 500 μM each for 25 min) of PGE1 or PGE2 with and without coadministration of 10 mM N(ω)-nitro-l-arginine, a nonspecific NOS inhibitor. N(ω)-nitro-l-arginine attenuated PGE1-mediated increases in CVC at all concentrations in young adults, whereas it reduced PGE2-mediated increases in CVC at lower concentrations (0.05-0.5 μM) in older adults (all P < 0.05). However, the magnitude of the PGE1- and PGE2-mediated increases in CVC did not differ between groups (all P > 0.05). Neither PGE1 nor PGE2 increased sweat rate at any of the administered concentrations for either the young or older adults (all P > 0.05). We show that although cutaneous vascular responsiveness to PGE1 and PGE2 is similar between young and older adults, the cutaneous vasodilator response is partially mediated through NOS albeit via low-to-high concentrations of PGE1 in young adults and low concentrations of PGE2 in older adults, respectively. We also show that in both young and older adults, PGE1 and PGE2 do not increase sweat rate under normothermic conditions.
Keywords: EP receptor; IP receptor; aging; cAMP; microcirculation; prostanoids; thermoregulation.
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