Postjunctional alpha 2-adrenoceptors mediate vasoconstriction in human subcutaneous resistance vessels.
1. In vitro studies have been performed on human medium-sized muscular arteries (internal diameter 1-4 mm) in a classical organ bath and with human subcutaneous resistance arteries (internal diameter 103-626 microns) in a microvascular myograph. 2. Although the medium-sized muscular arteries showed no response to either of the alpha 2-agonists B-HT 933 or UK 14304 in concentrations up to 10 microM, the subcutaneous resistance arteries from all regions examined showed well-pronounced and concentration-dependent responses to B-HT 933, the pD2 (-log EC50) being 5.11 +/- 0.09. 3. In the resistance arteries the alpha 2-antagonist yohimbine caused a parallel shift to the right of the B-HT 933 concentration-response curve; the yohimbine pA2 for the B-HT 933 receptor was 7.86 +/- 0.12. 4. There was an inverse relationship between the maximum response to B-HT 933 and the calibre of the resistance vessels. 5. These results indicate the presence of a postjunctional alpha 2-adrenoceptor in human subcutaneous resistance arteries and not in medium sized muscular arteries.
Nielsen
H
H
Department of Clinical Pharmacology, Queen Elisabeth The Queen Mother Wing, St. Mary's Hospital, London.
Thom
S M
SM
Hughes
A D
AD
Martin
G N
GN
Mulvany
M J
MJ
Sever
P S
PS
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000959:Antihypertensive Agents / Q000494:pharmacology; D001158:Arteries / Q000187:drug effects; D001381:Azepines / Q000494:pharmacology; D000068438:Brimonidine Tartrate; D017292:Doxazosin; D005260:Female; D006801:Humans; D066298:In Vitro Techniques; D008297:Male; D008875:Middle Aged; D009638:Norepinephrine / Q000494:pharmacology; D011224:Prazosin / Q000031:analogs & derivatives / Q000494:pharmacology; D011810:Quinoxalines / Q000494:pharmacology; D011942:Receptors, Adrenergic, alpha / Q000502:physiology*; D012039:Regional Blood Flow / Q000187:drug effects; D012867:Skin / Q000098:blood supply*; D014655:Vascular Resistance / Q000187:drug effects; D014661:Vasoconstriction; D014680:Veins / Q000187:drug effects; D015016:Yohimbine / Q000494:pharmacology
D000959:Antihypertensive Agents; D001381:Azepines; D011810:Quinoxalines; D011942:Receptors, Adrenergic, alpha; D015016:Yohimbine; D000068438:Brimonidine Tartrate; C015603:azepexole; D017292:Doxazosin; D009638:Norepinephrine; D011224:Prazosin