Post-ischemic vasodilation in the human forearm is dependent on
endothelium-derived nitric oxide.
Meredith, Ian T., Kristen E. Currie, Todd J. Anderson, Mary-Anne
Roddy, Peter Ganz, Mark A. Creager.
Vascular Medicine and Atherosclerosis Unit and Cardiac
Catheterization Laboratory, Cardiovascular Division, Brigham and
Women's Hospital and Harvard Medical School, Boston, MA 02115
APStracts 2:0440H, 1995.
Although endothelium-derived nitric oxide contributes to basal
vascular tone little is known about its role in regulating blood flow
during changes in metabolic supply and demand. We examined the
contribution of endothelium-derived nitric oxide to reactive
hyperemia in the forearm of 20 normal subjects (12F, 8M) aged 27+/- 4
years (mean+/-SD), using the nitric oxide synthase inhibitor, NG
-monomethyl-L-arginine (L-NMMA). Forearm ischemia was induced by
suprasystolic blood pressure cuff inflation for 5 minutes and the
subsequent hyperemic flow recorded for 5 minutes using venous
occlusion strain gauge plethysmography. The efficacy of nitric oxide
blockade was tested by comparing the dose-response relationship to
the endothelium-dependent agonist acetylcholine (3,10 and 30 mg/min)
before and after intra-arterial infusion of up to 2000 mg/min of L
-NMMA. L-NMMA produced a significant downward and rightward shift in
the dose-response relationship to acetylcholine and a 39% reduction
in response to the maximum dose (p<0.001). In the presence of L
-NMMA, peak hyperemic flow was reduced 16% (26.5+/-2.1 to 22.3+/-1.5
mls/min/100 mls of forearm <0.03) and the minimum forearm
vascular resistance was increased 22.8% (3.5+/-0.3 to 4.3+/-0.4
mmHg/mls/min/100 mls, p<0.02). Total hyperemia, calculated from
the area under the flow vs. time curve, at 1 and 5 minutes after cuff
release was 17% and 23% less, respectively. (13.6+/-1.2 vs. 11.3+/
-1.1 and 31.8+/-2.7 vs 24.6+/-1.8 mls/100mls, p<0.002) following
L-NMMA. These data suggest that endothelium-derived nitric oxide
plays a role in both reactive hyperemia and in the maintenance of the
hyperemic response following ischemia in the forearm.
Received 30 December 1994; accepted in final form 18 September
1995.
APS Manuscript Number H1149-4.
Article publication pending Am. J. Physiol. (Heart Circ. Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 6 November 95