alpha. -Adrenergic vasoconstriction and receptor subtypes in large coronary arteries of calves
- Massachusetts General Hospital, Boston (USA) New England Regional Primate Research Center, Southborough, MA (USA)
The authors investigated {alpha}-adrenoceptor subtype distribution in large coronary arteries from both functional and biochemical perspectives. The effects of intracoronary administration of the selective {alpha}{sub 1}-adrenoceptor agonist phenylephrine, of the selective {alpha}{sub 2}-adrenoceptor agonist B-HT 920 and of the mixed {alpha}{sub 1+2}-adrenoceptor agonist norepinephrine were examined on measurements of left circumflex coronary artery diameter in conscious calves. After {beta}-adrenergic blockade, equivalent reductions in large coronary artery diameter were observed with phenylephrine, B-HT, and norepinephrine. Phenylephrine-induced constrictions were abolished by prazosin, an {alpha}{sub 1}-selective antagonist, but unaffected by rauwolscine, an {alpha}{sub 2}-selective antagonist. Conversely, the B-HT-induced constriction was abolished by rauwolscine but unaffected by prazosin. Coronary constriction with norepinephrine was attenuated with either prazosin or rauwolscine and abolished by the two antagonists combined. Ligand-binding studies in which ({sup 3}H)prazosin and ({sup 3}H)rauwolscine and sarcolemmal membranes were used revealed an {alpha}{sub 1}-adrenoceptor density of 15 {plus minus} 3.1 fmol/mg protein with a dissociation constant (K{sub D}) of 0.7 {plus minus} 0.2 nM and an {alpha}{sub 2}-adrenoceptor density of 68 {plus minus} 5.1 fmol/mg protein, with a K{sub D} of 7.4 {plus minus} 1.2 nM. Thus large coronary arteries of the calf contain both {alpha}{sub 1}- and {alpha}{sub 2}-adrenoceptor subtypes, each of which elicits constriction of the large coronary artery in the conscious animal.
- OSTI ID:
- 6252522
- Journal Information:
- American Journal of Physiology; (USA), Vol. 255:6; ISSN 0002-9513
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
LIGANDS
CROSS-LINKING
RECEPTORS
TISSUE DISTRIBUTION
VASOCONSTRICTION
PHYSIOLOGY
CALVES
CORONARIES
TRITIUM COMPOUNDS
ANIMALS
ARTERIES
BLOOD VESSELS
BODY
CARDIOVASCULAR SYSTEM
CATTLE
CHEMICAL REACTIONS
DISTRIBUTION
DOMESTIC ANIMALS
HYDROGEN COMPOUNDS
MAMMALS
MEMBRANE PROTEINS
ORGANIC COMPOUNDS
ORGANS
POLYMERIZATION
PROTEINS
RUMINANTS
VERTEBRATES
551001* - Physiological Systems- Tracer Techniques