title: Mast cell degranulation and de novo histamine formation contribute to sustained postexercise vasodilation in humans.
abstract: In humans, acute aerobic exercise elicits a sustained postexercise vasodilation within previously active skeletal muscle. This response is dependent on activation of histamine H1and H2receptors, but the source of intramuscular histamine remains unclear. We tested the hypothesis that interstitial histamine in skeletal muscle would be increased with exercise and would be dependent on de novo formation via the inducible enzyme histidine decarboxylase and/or mast cell degranulation. Subjects performed 1 h of unilateral dynamic knee-extension exercise or sham (seated rest). We measured the interstitial histamine concentration and local blood flow (ethanol washout) via skeletal muscle microdialysis of the vastus lateralis. In some probes, we infused either α-fluoromethylhistidine hydrochloride (α-FMH), a potent inhibitor of histidine decarboxylase, or histamine H1/H2-receptor blockers. We also measured interstitial tryptase concentrations, a biomarker of mast cell degranulation. Compared with preexercise, histamine was increased after exercise by a change (Δ) of 4.2 ± 1.8 ng/ml (P< 0.05), but not when α-FMH was administered (Δ-0.3 ± 1.3 ng/ml,P= 0.9). Likewise, local blood flow after exercise was reduced to preexercise levels by both α-FMH and H1/H2blockade. In addition, tryptase was elevated during exercise by Δ6.8 ± 1.1 ng/ml (P< 0.05). Taken together, these data suggest that interstitial histamine in skeletal muscle increases with exercise and results from both de novo formation and mast cell degranulation. This suggests that exercise produces an anaphylactoid signal, which affects recovery, and may influence skeletal muscle blood flow during exercise.NEW & NOTEWORTHYBlood flow to previously active skeletal muscle remains elevated following an acute bout of aerobic exercise and is dependent on activation of histamine H1and H2receptors. The intramuscular source of histamine that drives this response to exercise has not been identified. Using intramuscular microdialysis in exercising humans, we show both mast cell degranulation and formation of histamine by histidine decarboxylase contributes to the histamine-mediated vasodilation that occurs following a bout of aerobic exercise.
authors: Department of Human Physiology, University of Oregon, Eugene, Oregon; and.
authors: Steven A
authors: SA
authors: Romero
authors: Department of Human Physiology, University of Oregon, Eugene, Oregon; and.
authors: Jennifer L
authors: JL
authors: McCord
authors: Department of Human Physiology, University of Oregon, Eugene, Oregon; and.
authors: Matthew R
authors: MR
authors: Ely
authors: Department of Human Physiology, University of Oregon, Eugene, Oregon; and.
authors: Dylan C
authors: DC
authors: Sieck
authors: Department of Human Physiology, University of Oregon, Eugene, Oregon; and.
authors: Tahisha M
authors: TM
authors: Buck
authors: Department of Human Physiology, University of Oregon, Eugene, Oregon; and.
authors: Meredith J
authors: MJ
authors: Luttrell
authors: Division of Medical Sciences, Northern Ontario School of Medicine, Sudbury, Ontario, Canada.
authors: David A
authors: DA
authors: MacLean
authors: Department of Human Physiology, University of Oregon, Eugene, Oregon; and halliwil@uoregon.edu.
authors: John R
authors: http://orcid.org/0000-0003-3001-1715
authors: JR
authors: Halliwill
mesh_terms: D001783:Blood Flow Velocity / Q000502:physiology*; D015550:Cell Degranulation / Q000502:physiology*; D015444:Exercise / Q000502:physiology*; D005260:Female; D006632:Histamine / Q000378:metabolism*; D006801:Humans; D008297:Male; D008407:Mast Cells / Q000502:physiology*; D018482:Muscle, Skeletal / Q000098:blood supply / Q000166:cytology / Q000502:physiology*; D014664:Vasodilation / Q000502:physiology*; D055815:Young Adult
chemical_list: D006632:Histamine
keywords: extracellular fluid; histamine; microdialysis; postexercise hypotension; regional blood flow