title: H2-receptor-mediated vasodilation contributes to postexercise hypotension.
abstract: The early (approximately 30 min) postexercise hypotension response after a session of aerobic exercise is due in part to H1-receptor-mediated vasodilation. The purpose of this study was to determine the potential contribution of H2-receptor-mediated vasodilation to postexercise hypotension. We studied 10 healthy normotensive men and women (ages 23.7 +/- 3.4 yr) before and through 90 min after a 60-min bout of cycling at 60% peak O2 uptake on randomized control and H2-receptor antagonist days (300 mg oral ranitidine). Arterial pressure (automated auscultation), cardiac output (acetylene washin) and femoral blood flow (Doppler ultrasound) were measured. Vascular conductance was calculated as flow/mean arterial pressure. Sixty minutes postexercise on the control day, femoral (delta62.3 +/- 15.6%, where Delta is change; P < 0.01) and systemic (delta13.8 +/- 5.3%; P = 0.01) vascular conductances were increased, whereas mean arterial pressure was reduced (Delta-6.7 +/- 1.1 mmHg; P < 0.01). Conversely, 60 min postexercise with ranitidine, femoral (delta9.4 +/- 9.2%; P = 0.34) and systemic (delta-2.8 +/- 4.8%; P = 0.35) vascular conductances were not elevated and mean arterial pressure was not reduced (delta-2.2 +/- 1.3 mmHg; P = 0.12). Furthermore, postexercise femoral and systemic vascular conductances were lower (P < 0.05) and mean arterial pressure was higher (P = 0.01) on the ranitidine day compared with control. Ingestion of ranitidine markedly reduces vasodilation after exercise and blunts postexercise hypotension, suggesting H2-receptor-mediated vasodilation contributes to postexercise hypotension.
authors.affiliation: Department of Human Physiology, 122 Esslinger Hall, 1240 University of Oregon, Eugene, Oregon 97403-1240, USA.
authors.forename: Jennifer L
authors.initials: JL
authors.lastname: McCord
authors.forename: Julie M
authors.initials: JM
authors.lastname: Beasley
authors.forename: John R
authors.initials: JR
authors.lastname: Halliwill
mesh_terms: D000222:Adaptation, Physiological / Q000187:drug effects; D000328:Adult; D001783:Blood Flow Velocity / Q000187:drug effects; D001794:Blood Pressure / Q000187:drug effects; D005080:Exercise Test / Q000009:adverse effects*; D005260:Female; D006635:Histamine H2 Antagonists / Q000008:administration & dosage; D006801:Humans; D007022:Hypotension / Q000209:etiology / Q000503:physiopathology*; D008297:Male; D018482:Muscle, Skeletal / Q000098:blood supply* / Q000187:drug effects / Q000503:physiopathology*; D005082:Physical Exertion; D011899:Ranitidine / Q000008:administration & dosage; D011970:Receptors, Histamine H2 / Q000378:metabolism*; D014655:Vascular Resistance / Q000187:drug effects; D014664:Vasodilation
chemical_list: D006635:Histamine H2 Antagonists; D011970:Receptors, Histamine H2; D011899:Ranitidine