title: Halothane effect on beta-adrenergic receptors in canine myocardium.
abstract: Halothane depresses the inotropic state of the heart, possibly by decreasing the rate of formation of cyclic 3',5'-adenosine monophosphate (cAMP) through depression of the activity of adenylate cyclase, the cAMP-generating enzyme. As catecholamines regulate the inotropic state and adenylate cyclase activity by binding to myocardial beta-adrenergic receptors, the effect of halothane on binding to these receptors was studied to determine whether this was a site of halothane effect. Beta-adrenergic binding was measured at binding equilibrium in vitro in a canine myocardial membrane preparation in the absence and presence of halothane, 3 to 5 vol%, using as the radioligand 3H-dihydroalprenolol (3H-DHA), a beta-adrenergic antagonist with high affinity and radioactivity. In addition, the effect of halothane on the binding of l-isoproterenol, a beta-adrenergic agonist, was measured by displacement of 3H-DHA. The results indicate that halothane has no effect on either the affinity of canine myocardial beta-adrenergic receptors for 3H-DHA or l-isoproterenol, nor does it alter the number of available receptors at binding equilibrium.
mesh_terms: D000262:Adenylyl Cyclases / Q000378:metabolism; D000818:Animals; D002462:Cell Membrane / Q000378:metabolism; D000242:Cyclic AMP / Q000378:metabolism; D004082:Dihydroalprenolol / Q000378:metabolism; D004285:Dogs; D005260:Female; D006160:Guanosine Triphosphate / Q000494:pharmacology; D006221:Halothane / Q000494:pharmacology*; D006321:Heart / Q000187:drug effects*; D007545:Isoproterenol / Q000494:pharmacology; D008297:Male; D009206:Myocardium / Q000378:metabolism; D011941:Receptors, Adrenergic / Q000187:drug effects*; D011943:Receptors, Adrenergic, beta / Q000187:drug effects*
chemical_list: D011941:Receptors, Adrenergic; D011943:Receptors, Adrenergic, beta; D004082:Dihydroalprenolol; D006160:Guanosine Triphosphate; D000242:Cyclic AMP; D000262:Adenylyl Cyclases; D007545:Isoproterenol; D006221:Halothane