Effect of clenbuterol on beta-adrenoceptors and adenylate cyclase activity in smooth muscle and epithelium of the trachea of calves.
A potent beta-agonist (clenbuterol) was administered perorally to young calves for 50 days. After this period the animals were slaughtered and beta-adrenoceptor density, ligand affinity, and basal and stimulated adenylate cyclase activities were studied in smooth muscle and epithelium of the trachea. Although the density of lung beta-adrenoceptors was down regulated by clenbuterol, cAMP production remained constant (epithelium) or even increased (smooth muscle). Therefore desensitization of beta-adrenoceptors in the trachea was not observed. This might be a reason for the effectiveness of long-term treatment with beta-agonists.
Roets
E
E
Department of Veterinary Physiology, Faculty of Veterinary Medicine, University of Ghent, Belgium.
Burvenich
C
C
D000262:Adenylyl Cyclases / Q000378:metabolism*; D000284:Administration, Oral; D000818:Animals; D002417:Cattle; D002462:Cell Membrane / Q000378:metabolism; D002976:Clenbuterol / Q000008:administration & dosage / Q000494:pharmacology*; D004082:Dihydroalprenolol / Q000378:metabolism; D009130:Muscle, Smooth / Q000187:drug effects* / Q000378:metabolism; D011943:Receptors, Adrenergic, beta / Q000378:metabolism*; D014132:Trachea / Q000187:drug effects* / Q000378:metabolism
D011943:Receptors, Adrenergic, beta; D004082:Dihydroalprenolol; D000262:Adenylyl Cyclases; D002976:Clenbuterol