title: Cardiovascular and plasma catecholamine response to static exercise in normotensive blacks and whites.
abstract: OBJECTIVE
  The objectives of the present study were (1) to evaluate the pressor response to an isometric handgrip exercise in normotensive black and white males; (2) to measure plasma catecholamine levels pre- and post-exercise, as an index of sympathetic nervous system activity; and (3) to quantify the pressor response to bolus intravenous injections of phenylephrine (an alpha-specific agonist).
  
  
  METHODS
  Cardiovascular and catecholamine responses to an isometric handgrip exercise (3 minutes at 30% MVC) were measured in 15 normotensive blacks and whites. In another phase of the study, pressor responses to bolus injections of phenylephrine were assessed to evaluate alpha-adrenergic sensitivity.
  
  
  RESULTS
  The blood pressure in the blacks increased from 119/69 to 160/120 mm HG during isometric exercise, while in the whites it increased from 118/67 to 153/110 mm HG. The blacks exhibited a greater diastolic blood pressure reactivity, as evidenced by a significant race x time interaction (p < 0.05). The heart rate responses were not significantly different between the two groups. The plasma levels of norepinephrine were similar at rest, but were 25% lower in the blacks than in the whites following isometric exercise (p < 0.01). Black subjects also demonstrated an increased pressor response to intravenous injections of phenylephrine at rest (p < 0.05).
  
  
  CONCLUSIONS
  The enhanced vascular sensitivity to norepinephrine may have contributed to the greater exercise pressor response in the blacks.
authors.affiliation: Exercise Science Unit, University of Tennessee-Knoxville, USA.
authors.forename: W J
authors.initials: WJ
authors.lastname: Duey
authors.forename: D R
authors.initials: DR
authors.lastname: Bassett
authors.forename: A J
authors.initials: AJ
authors.lastname: Walker
authors.forename: D J
authors.initials: DJ
authors.lastname: Torok
authors.forename: E T
authors.initials: ET
authors.lastname: Howley
authors.forename: D
authors.initials: D
authors.lastname: Ely
authors.forename: M O
authors.initials: MO
authors.lastname: Pease
mesh_terms: D000316:Adrenergic alpha-Agonists / Q000494:pharmacology; D000328:Adult; D044383:Black People; D001794:Blood Pressure / Q000502:physiology*; D004837:Epinephrine / Q000097:blood*; D015444:Exercise / Q000502:physiology*; D018737:Hand Strength; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D007275:Injections, Intravenous; D008297:Male; D009638:Norepinephrine / Q000097:blood*; D010656:Phenylephrine / Q000494:pharmacology; D012016:Reference Values; D013564:Sympathetic Nervous System / Q000502:physiology; D014662:Vasoconstrictor Agents / Q000097:blood*; D044465:White People
chemical_list: D000316:Adrenergic alpha-Agonists; D014662:Vasoconstrictor Agents; D010656:Phenylephrine; D009638:Norepinephrine; D004837:Epinephrine