Impact of shear rate modulation on vascular function in humans.
Shear stress is an important stimulus to arterial adaptation in response to exercise and training in humans. We recently observed significant reverse arterial flow and shear during exercise and different antegrade/retrograde patterns of shear and flow in response to different types of exercise. The purpose of this study was to simultaneously examine flow-mediated dilation, a largely NO-mediated vasodilator response, in both brachial arteries of healthy young men before and after 30-minute interventions consisting of bilateral forearm heating, recumbent leg cycling, and bilateral handgrip exercise. During each intervention, a cuff inflated to 60 mm Hg was placed on 1 arm to unilaterally manipulate the shear rate stimulus. In the noncuffed arm, antegrade flow and shear increased similarly in response to each intervention (ANOVA; P<0.001, no interaction between interventions; P=0.71). Baseline flow-mediated dilation (4.6%, 6.9%, and 6.7%) increased similarly in response to heating, handgrip, and cycling (8.1%, 10.4%, and 8.9%, ANOVA; P<0.001, no interaction; P=0.89). In contrast, cuffed arm antegrade shear rate was lower than in the noncuffed arm for all of the conditions (P<0.05), and the increase in flow-mediated dilation was abolished in this arm (4.7%, 6.7%, and 6.1%; 2-way ANOVA: all conditions interacted P<0.05). These results suggest that differences in the magnitude of antegrade shear rate transduce differences in endothelial vasodilator function in humans, a finding that may have relevance for the impact of different exercise interventions on vascular adaptation in humans.
Tinken
Toni M
TM
Research Institute for Sport and Exercise Science, Liverpool John Moores University, 15-21 Webster St, Liverpool L3 2ET, United Kingdom.
Thijssen
Dick H J
DH
Hopkins
Nicola
N
Black
Mark A
MA
Dawson
Ellen A
EA
Minson
Christopher T
CT
Newcomer
Sean C
SC
Laughlin
M Harold
MH
Cable
N Timothy
NT
Green
Daniel J
DJ
D000222:Adaptation, Physiological; D000328:Adult; D000704:Analysis of Variance; D001783:Blood Flow Velocity / Q000502:physiology*; D001794:Blood Pressure / Q000502:physiology*; D001795:Blood Pressure Determination; D001916:Brachial Artery / Q000502:physiology*; D005080:Exercise Test / Q000379:methods*; D005542:Forearm / Q000098:blood supply; D018737:Hand Strength / Q000502:physiology; D006439:Hemodynamics / Q000502:physiology; D006801:Humans; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000502:physiology; D010101:Oxygen Consumption; D011336:Probability; D012016:Reference Values; D012039:Regional Blood Flow / Q000502:physiology; D012494:Sampling Studies; D012680:Sensitivity and Specificity; D033081:Shear Strength / Q000502:physiology*; D014661:Vasoconstriction / Q000502:physiology; D014664:Vasodilation / Q000502:physiology