Identification of beta-adrenergic receptor subtypes mediating relaxation in isolated equine ileum.
OBJECTIVE
To identify beta-adrenergic receptor subtypes in ileum smooth muscle of the horse.


METHODS
Isolated strips of equine longitudinal ileum smooth muscle and membrane preparations from smooth muscle of the intestinal wall.


METHODS
Functional assays and radioligand binding assays.


RESULTS
Relaxation of ileum longitudinal smooth muscle proved to be mainly caused by stimulation of beta-atypical and beta 2-adrenergic receptors. Binding studies on cell membranes indicated that the total beta-adrenergic receptors population consists of 54% beta-atypical, 34% beta 2- and 12% beta 1-subtypes.


CONCLUSIONS
The data suggest that sympathetic relaxation of equine ileum smooth muscle depends mainly on beta-atypical receptor subtypes activation, with a minor contribution by beta 2-subtypes.


CONCLUSIONS
The important role of beta-atypical adrenergic receptor subtypes in the relaxation of equine ileum suggests possible clinical use of selective beta-atypical receptor agonists to control intestinal disturbances.
Re
G
G
Department of Animal Pathology, University of Turin, Italy.
Belloli
C
C
Badino
P
P
Arioli
F
F
Novelli
A
A
Girardi
C
C
Beretta
C
C
D000318:Adrenergic beta-Agonists / Q000378:metabolism / Q000494:pharmacology; D000319:Adrenergic beta-Antagonists / Q000378:metabolism / Q000494:pharmacology; D000818:Animals; D001667:Binding, Competitive; D002462:Cell Membrane / Q000737:chemistry / Q000378:metabolism / Q000648:ultrastructure; D005260:Female; D006736:Horses / Q000502:physiology*; D007082:Ileum / Q000737:chemistry / Q000166:cytology / Q000502:physiology*; D008297:Male; D009126:Muscle Relaxation / Q000502:physiology*; D009130:Muscle, Smooth / Q000737:chemistry / Q000502:physiology* / Q000648:ultrastructure; D011412:Propanolamines / Q000378:metabolism / Q000494:pharmacology; D011485:Protein Binding; D011869:Radioligand Assay / Q000379:methods / Q000662:veterinary; D011943:Receptors, Adrenergic, beta / Q000032:analysis / Q000378:metabolism / Q000502:physiology*; D018342:Receptors, Adrenergic, beta-1 / Q000032:analysis / Q000378:metabolism / Q000502:physiology; D018343:Receptors, Adrenergic, beta-2 / Q000032:analysis / Q000378:metabolism / Q000502:physiology; D014316:Tritium
D000318:Adrenergic beta-Agonists; D000319:Adrenergic beta-Antagonists; D011412:Propanolamines; D011943:Receptors, Adrenergic, beta; D018342:Receptors, Adrenergic, beta-1; D018343:Receptors, Adrenergic, beta-2; D014316:Tritium; C033394:CGP 12177