B-48 Free Communication/Slide - Blood Flow: MAY 30, 2007 3:15 PM - 5:00 PM ROOM: 345
PURPOSE: Endurance training improves endothelium-dependent vasodilation. Yet it does not increase basal leg blood flow. We determined effects of endurance training on basal blood flow and α-adrenergic vasoconstriction and nitric oxide release in aged humans.
METHODS: Seven apparently healthy adults (60±3 yr) underwent systemic α-adrenergic blockade (with phentolamine) and nitric oxide synthase (NOS) inhibition using NG-monomethyl-L-arginine in sequence before and after the 3-month aerobic exercise intervention.
RESULTS: Baseline femoral artery blood flow (via Doppler ultrasound) did not change significantly with the exercise training intervention (354±29 to 335±34 ml/ min). Before the training intervention, femoral artery blood flow increased 32% with α-adrenergic blockade (P<0.05), and the addition of NOS blockade did not affect femoral artery blood flow (ns). After the training intervention, femoral artery blood flow increased 47% with ?-adrenergic blockade (P<0.01) and then reduced 18±7% with L-NMMA administration (P<0.05). Leg vascular conductance showed a greater α-adrenergic blockade-induced vasodilation (50±16 to 86±13%, P<0.05) as well as NOS inhibition-induced vasoconstriction (−15±8 to −38±7%, P<0.05) after the training.
CONCLUSIONS: These results suggest that endurance training enhances both basal α-adrenergic vasoconstriction and NO bioavailability in older adults and that basal limb blood flow does not change with exercise training because of these antagonistic effects of sympathetic activation and endothelium-derived vasodilation on the vasculature.