Nitric oxide and passive limb movement: a new approach to assess vascular function.
Passive limb movement elicits a robust increase in limb blood flow (LBF) and limb vascular conductance (LVC), but the peripheral vascular mechanisms associated with this increase in LBF and LVC are unknown. This study sought to determine the contribution of nitric oxide (NO) to movement-induced LBF and LVC and document the potential for passive-limb movement to assess NO-mediated vasodilatation and therefore NO bioavailability. Six subjects underwent passive knee extension with and without nitric oxide synthase (NOS) inhibition via intra-arterial infusion of N(G)-monomethyl-L-arginine (L-NMMA). LBF was determined second-by-second by Doppler ultrasound, and central haemodynamics were measured by finger photoplethysmography. Although L-NMMA did not alter the immediate increase (initial ∼9 s) in LBF and LVC, NOS blockade attenuated the peak increase in LBF (control: 653 ± 81; L-NMMA: 399 ± 112 ml(−1) min(−1), P = 0.03) and LVC (control: 7.5 ± 0.8; L-NMMA: 4.1 ± 1.1 ml min(−1) mmHg(−1), P = 0.02) and dramatically reduced the overall vasodilatory and hyperaemic response (area under the curve) by nearly 80% (LBF: control: 270 ± 51; L-NMMA: 75 ± 32 ml, P = 0.001; LVC: control: 2.9 ± 0.5; L-NMMA: 0.8 ± 0.3 ml mmHg(−1), P < 0.001). Passive movement in control and L-NMMA trials evoked similar increases in heart rate, stroke volume, cardiac output and a reduction in mean arterial pressure. As movement-induced increases in LBF and LVC are predominantly NO dependent, passive limb movement appears to have significant promise as a new approach to assess NO-mediated vascular function, an important predictor of cardiovascular disease risk.
Geriatric Research, Education, and Clinical Center, George E. Whalen VA Medical Center, Salt Lake City, UT 84148, USA. joel.trinity@utah.edu
Joel D
JD
Trinity
H Jonathan
HJ
Groot
Gwenael
G
Layec
Matthew J
MJ
Rossman
Stephen J
SJ
Ives
Sean
S
Runnels
Ben
B
Gmelch
Amber
A
Bledsoe
Russell S
RS
Richardson
D000328:Adult; D001794:Blood Pressure / Q000187:drug effects; D002302:Cardiac Output / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005263:Femoral Artery / Q000502:physiology; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D006940:Hyperemia / Q000503:physiopathology; D007866:Leg / Q000098:blood supply / Q000502:physiology*; D008297:Male; D009068:Movement / Q000502:physiology*; D009569:Nitric Oxide / Q000502:physiology*; D052250:Nitric Oxide Synthase Type III / Q000037:antagonists & inhibitors / Q000502:physiology; D012039:Regional Blood Flow / Q000187:drug effects; D014664:Vasodilation / Q000187:drug effects / Q000502:physiology; D055815:Young Adult; D019323:omega-N-Methylarginine / Q000494:pharmacology
D004791:Enzyme Inhibitors; D019323:omega-N-Methylarginine; D009569:Nitric Oxide; C496314:NOS3 protein, human; D052250:Nitric Oxide Synthase Type III