Regulation of beta-adrenoceptors by catecholamines in the rabbit skeletal muscle.
(-)-[125I]Cyanopindolol (ICYP) was used to characterise beta-adrenoceptors in the gastrocnemius muscle of the rabbit. The binding of ICYP was saturable. The KI value for the selective beta 2-adrenoceptor antagonist, ICI 118551, was 0.16 +/- 0.01 nM (mean +/- S.E.M) and for the selective beta 1-adrenoceptor antagonist, metoprolol, was 300.1 +/- 33.3 nM. Hofstee plots for both antagonists were linear indicating the presence of homogeneous beta 2-adrenoceptors in the skeletal muscle of the rabbit. In gastrocnemius muscles obtained from rabbits chronically pretreated in vivo with vehicle (0.1% ascorbic acid), adrenaline (40-50 nmol.kg-1.h-1) or noradrenaline (80-100 nmol.kg-1.h-1) via osmotic mini-pumps implanted for 10 days, the Bmax values were 44 +/- 3, 25 +/- 4 (P less than 0.05) and 41 +/- 7 (fmol.mg-1 protein) and KD values were 7.3 +/- 0.9, 6.3 +/- 0.8 and 9.3 +/- 2.5 (pM), respectively. Thus pretreatment with the circulating hormone adrenaline but not noradrenaline down-regulated the number of skeletal muscle beta 2-adrenoceptors but did not influence the affinity.
Elfellah
M S
MS
Department of Materia Medica, University of Glasgow, Stobhill General Hospital, U.K.
Deighton
N
N
Reid
J L
JL
D000319:Adrenergic beta-Antagonists / Q000494:pharmacology; D000818:Animals; D004837:Epinephrine / Q000502:physiology*; D008297:Male; D008790:Metoprolol / Q000494:pharmacology; D009132:Muscles / Q000187:drug effects*; D009638:Norepinephrine / Q000502:physiology*; D010869:Pindolol / Q000031:analogs & derivatives / Q000494:pharmacology; D011412:Propanolamines / Q000494:pharmacology; D011817:Rabbits; D011943:Receptors, Adrenergic, beta / Q000187:drug effects* / Q000502:physiology
D000319:Adrenergic beta-Antagonists; D011412:Propanolamines; D011943:Receptors, Adrenergic, beta; C026777:ICI 118551; C047975:cyanopindolol; D010869:Pindolol; D008790:Metoprolol; D009638:Norepinephrine; D004837:Epinephrine