Alpha-adrenoceptors in human resistance arteries from colon, pericardial fat, and skeletal muscle.
Human resistance arteries (144-332 microns diam) from colon, pericardial fat, and skeletal muscle were mounted in a myograph for measurements of isometric contractions under conditions of partial depolarization by potassium chloride. In all preparations, both phenylephrine (alpha 1-selective agonist) and B-HT 933 (alpha 2-selective agonist) evoked concentration-dependent contractions that were antagonized by the alpha 1-selective antagonist prazosin (10(-8) M) and the alpha 2-selective antagonist yohimbine (10(-7) M), respectively. The affinities (expressed as pKB values) of prazosin for the receptor mediating the responses to phenylephrine were 8.88-9.41, whereas the affinities of yohimbine for the receptor mediating the responses to B-HT 933 were 7.71-7.97. Norepinephrine (mixed alpha 1-agonist/alpha 2-agonist) also elicited concentration-dependent responses that were modestly, but significantly, antagonized by prazosin alone and yohimbine alone at the above-mentioned concentrations. The two antagonists in combination, however, effectively antagonized the responses to this agonist. These findings strongly suggest the presence of functional, postjunctional alpha 1- and alpha 2-adrenoceptors in isolated human resistance arteries from colon, pericardial fat, and skeletal muscle and that responses to norepinephrine in these vessels are mediated by both alpha-adrenoceptor subtypes.
Nielsen
H
H
Institute of Pharmacology, University of Aarhus, Denmark.
Hasenkam
J M
JM
Pilegaard
H K
HK
Mortensen
F V
FV
Mulvany
M J
MJ
D000273:Adipose Tissue / Q000098:blood supply*; D000316:Adrenergic alpha-Agonists / Q000494:pharmacology; D000368:Aged; D001158:Arteries / Q000187:drug effects / Q000502:physiology* / Q000503:physiopathology; D001381:Azepines / Q000494:pharmacology; D001794:Blood Pressure; D003106:Colon / Q000098:blood supply*; D005260:Female; D006801:Humans; D066298:In Vitro Techniques; D007537:Isometric Contraction / Q000187:drug effects*; D008297:Male; D008875:Middle Aged; D009130:Muscle, Smooth / Q000098:blood supply; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000502:physiology* / Q000503:physiopathology; D009132:Muscles / Q000098:blood supply*; D009638:Norepinephrine / Q000494:pharmacology / Q000502:physiology*; D010656:Phenylephrine / Q000494:pharmacology; D011224:Prazosin / Q000494:pharmacology*; D011943:Receptors, Adrenergic, beta / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D014655:Vascular Resistance / Q000187:drug effects; D015016:Yohimbine / Q000494:pharmacology*
D000316:Adrenergic alpha-Agonists; D001381:Azepines; D011943:Receptors, Adrenergic, beta; D010656:Phenylephrine; D015016:Yohimbine; C015603:azepexole; D009638:Norepinephrine; D011224:Prazosin