title: Vascular responses of the extremities to transdermal application of vasoactive agents in Caucasian and African descent individuals.
abstract: OBJECTIVE
  Individuals of African descent (AFD) are more susceptible to non-freezing cold injury than Caucasians (CAU) which may be due, in part, to differences in the control of skin blood flow. We investigated the skin blood flow responses to transdermal application of vasoactive agents.
  
  
  METHODS
  Twenty-four young males (12 CAU and 12 AFD) undertook three tests in which iontophoresis was used to apply acetylcholine (ACh 1 w/v %), sodium nitroprusside (SNP 0.01 w/v %) and noradrenaline (NA 0.5 mM) to the skin. The skin sites tested were: volar forearm, non-glabrous finger and toe, and glabrous finger (pad) and toe (pad).
  
  
  RESULTS
  In response to SNP on the forearm, AFD had less vasodilatation for a given current application than CAU (P = 0.027-0.004). ACh evoked less vasodilatation in AFD for a given application current in the non-glabrous finger and toe compared with CAU (P = 0.043-0.014) with a lower maximum vasodilatation in the non-glabrous finger (median [interquartile], AFD n = 11, 41[234] %, CAU n = 12, 351[451] %, P = 0.011) and non-glabrous toe (median [interquartile], AFD n = 9, 116[318] %, CAU n = 12, 484[720] %, P = 0.018). ACh and SNP did not elicit vasodilatation in the glabrous skin sites of either group. There were no ethnic differences in response to NA.
  
  
  CONCLUSIONS
  AFD have an attenuated endothelium-dependent vasodilatation in non-glabrous sites of the fingers and toes compared with CAU. This may contribute to lower skin temperature following cold exposure and the increased risk of cold injuries experienced by AFD.
authors.affiliation: Extreme Environments Laboratory, Department of Sport and Exercise Science, University of Portsmouth, Portsmouth, PO1 2ER, UK, matthew.maley@port.ac.uk.
authors.forename: Matthew J
authors.initials: MJ
authors.lastname: Maley
authors.forename: James R
authors.initials: JR
authors.lastname: House
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Tipton
authors.forename: Clare M
authors.initials: CM
authors.lastname: Eglin
mesh_terms: D000109:Acetylcholine / Q000494:pharmacology; D000279:Administration, Cutaneous; D000328:Adult; D044383:Black People; D003080:Cold Temperature; D004305:Dose-Response Relationship, Drug; D004730:Endothelium, Vascular / Q000187:drug effects; D005121:Extremities / Q000098:blood supply*; D006801:Humans; D007478:Iontophoresis; D008297:Male; D009599:Nitroprusside / Q000494:pharmacology; D009638:Norepinephrine / Q000494:pharmacology; D012039:Regional Blood Flow / Q000187:drug effects*; D012867:Skin / Q000098:blood supply / Q000187:drug effects; D012881:Skin Temperature / Q000187:drug effects; D014662:Vasoconstrictor Agents / Q000008:administration & dosage / Q000494:pharmacology*; D014664:Vasodilation / Q000187:drug effects; D014665:Vasodilator Agents / Q000008:administration & dosage / Q000494:pharmacology*; D044465:White People; D055815:Young Adult
chemical_list: D014662:Vasoconstrictor Agents; D014665:Vasodilator Agents; D009599:Nitroprusside; D000109:Acetylcholine; D009638:Norepinephrine
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