Potency of adrenaline and noradrenaline for beta-adrenergic proton extrusion from red cells of rainbow trout, Salmo gairdneri.
The red cell adrenoceptor affinity for the unspecific agonists adrenaline and noradrenaline and the specific beta-agonist isoprenaline was studied in vitro on whole blood of rainbow trout, Salmo gairdneri at 15 degrees C. The erythrocytic adrenoceptors could be pharmacologically characterized as beta-receptors of the 'noradrenaline'-type (beta 1-type), with an order of potency of isoprenaline greater than noradrenaline much greater than adrenaline. The adrenoceptor affinities, expressed as agonist concentrations for 50% response (EC50), were 1.3 X 10(-8) and 7.6 X 10(-7) mol l-1 for noradrenaline and adrenaline, respectively. Winter fish showed a red cell adrenergic response identical to that of summer-acclimated fish. It is concluded that most red cell beta-adrenergic responses in vivo are exclusively elicited by noradrenaline.
Tetens
V
V
Department of Zoophysiology, University of Aarhus, Denmark.
Lykkeboe
G
G
Christensen
N J
NJ
D000818:Animals; D004837:Epinephrine / Q000097:blood / Q000494:pharmacology*; D004912:Erythrocytes / Q000187:drug effects / Q000378:metabolism*; D007545:Isoproterenol / Q000494:pharmacology*; D007700:Kinetics; D009638:Norepinephrine / Q000097:blood / Q000494:pharmacology*; D011943:Receptors, Adrenergic, beta / Q000187:drug effects / Q000502:physiology*; D012487:Salmonidae / Q000097:blood*; D014337:Trout / Q000097:blood*
D011943:Receptors, Adrenergic, beta; D007545:Isoproterenol; D009638:Norepinephrine; D004837:Epinephrine