Effect of chronic pretreatment of guinea-pigs with beta-adrenoceptor agonists on the Na+,K(+)-pump in skeletal muscle.
1. The Bmax values for the radioligand [3H]-ouabain in gastrocnemius muscle membranes from guinea-pigs pretreated with vehicle (0.9% saline, 0.1% ascorbic acid), isoprenaline (50 micrograms kg-1) or terbutaline (125 micrograms kg-1) subcutaneously three times daily for 7 days were 5.3 +/- 0.6; 3.1 +/- 0.4 (P less than 0.05) and 2.0 +/- 0.2 pmol mg-1 protein (P less than 0.01) (means +/- S.E.M.) respectively. Thus chronic pretreatment of the guinea-pigs with isoprenaline or terbutaline reduced the density of [3H]-ouabain binding sites by 40 and 60% respectively. 2. The ouabain-sensitive uptake of 86Rb in intact soleus muscles from control and terbutaline pretreated animals were 10.8 +/- 1.2 and 9.0 +/- mmol g-1 wet tissue 20 min-1 respectively. Pretreatment of guinea-pigs with terbutaline did not therefore significantly alter ouabain-sensitive uptake of 86Rb (P greater than 0.1). 3. The results support a close relationship between regulation of beta-adrenoceptors and [3H]-ouabain binding sites. 4. Additional investigations are required to confirm further the dissociation between the function of the pump and the ouabain binding sites measured under the present experimental conditions.
Elfellah
M S
MS
Department of Materia Medica, Stobhill General Hospital, University of Glasgow, UK.
Reid
J L
JL
D000318:Adrenergic beta-Agonists / Q000494:pharmacology*; D000818:Animals; D001665:Binding Sites; D015536:Down-Regulation; D006168:Guinea Pigs; D007545:Isoproterenol / Q000494:pharmacology; D007700:Kinetics; D008297:Male; D009132:Muscles / Q000187:drug effects* / Q000201:enzymology / Q000502:physiology / Q000648:ultrastructure; D010042:Ouabain / Q000378:metabolism; D011188:Potassium / Q000378:metabolism; D012414:Rubidium Radioisotopes; D012964:Sodium / Q000378:metabolism; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*; D013726:Terbutaline / Q000494:pharmacology; D013997:Time Factors; D014316:Tritium
D000318:Adrenergic beta-Agonists; D012414:Rubidium Radioisotopes; D014316:Tritium; D010042:Ouabain; D012964:Sodium; D000254:Sodium-Potassium-Exchanging ATPase; D007545:Isoproterenol; D013726:Terbutaline; D011188:Potassium