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Sympathetic activation increases NO release from eNOS but neither eNOS nor nNOS play an essential role in exercise hyperemia in the human forearm.
- Source :
-
American journal of physiology. Heart and circulatory physiology [Am J Physiol Heart Circ Physiol] 2013 May; Vol. 304 (9), pp. H1225-30. Date of Electronic Publication: 2013 Feb 22. - Publication Year :
- 2013
-
Abstract
- Nitric oxide (NO) release from endothelial NO synthase (eNOS) and/or neuronal NO synthase (nNOS) could be modulated by sympathetic nerve activity and contribute to increased blood flow after exercise. We examined the effects of brachial-arterial infusion of the nNOS selective inhibitor S-methyl-l-thiocitrulline (SMTC) and the nonselective NOS inhibitor N(G)-monomethyl-l-arginine (l-NMMA) on forearm arm blood flow at rest, during sympathetic activation by lower body negative pressure, and during lower body negative pressure immediately after handgrip exercise. Reduction in forearm blood flow by lower body negative pressure during infusion of SMTC was not significantly different from that during vehicle (-28.5 ± 4.02 vs. -34.1 ± 2.96%, respectively; P = 0.32; n = 8). However, l-NMMA augmented the reduction in forearm blood flow by lower body negative pressure (-44.2 ± 3.53 vs. -23.4 ± 5.71%; n = 8; P < 0.01). When lower body negative pressure was continued after handgrip exercise, there was no significant effect of either l-NMMA or SMTC on forearm blood flow immediately after low-intensity exercise (P = 0.91 and P = 0.44 for l-NMMA vs. saline and SMTC vs. saline, respectively; each n = 10) or high-intensity exercise (P = 0.46 and P = 0.68 for l-NMMA vs. saline and SMTC vs. saline, respectively; each n = 10). These results suggest that sympathetic activation increases NO release from eNOS, attenuating vasoconstriction. Dysfunction of eNOS could augment vasoconstrictor and blood pressure responses to sympathetic activation. However, neither eNOS nor nNOS plays an essential role in postexercise hyperaemia, even in the presence of increased sympathetic activation.
- Subjects :
- Adult
Blood Pressure
Citrulline analogs & derivatives
Citrulline pharmacology
Forearm innervation
Hand Strength
Humans
Hyperemia enzymology
Hyperemia physiopathology
Male
Nitric Oxide Synthase Type I antagonists & inhibitors
Nitric Oxide Synthase Type III antagonists & inhibitors
Regional Blood Flow
Thiourea analogs & derivatives
Thiourea pharmacology
Vasoconstriction
omega-N-Methylarginine pharmacology
Forearm blood supply
Hyperemia metabolism
Nitric Oxide metabolism
Nitric Oxide Synthase Type I metabolism
Nitric Oxide Synthase Type III metabolism
Physical Exertion
Sympathetic Nervous System physiopathology
Subjects
Details
- Language :
- English
- ISSN :
- 1522-1539
- Volume :
- 304
- Issue :
- 9
- Database :
- MEDLINE
- Journal :
- American journal of physiology. Heart and circulatory physiology
- Publication Type :
- Academic Journal
- Accession number :
- 23436331
- Full Text :
- https://doi.org/10.1152/ajpheart.00783.2012