Desensitization by terbutaline of beta-adrenoceptors in the guinea-pig soleus muscle: biochemical alterations associated with functional changes.
1 The effects of adrenaline and terbutaline on cyclic adenosine 3',5'-monophosphate (cyclic AMP) content, 22Na-efflux, 42K-influx and subtetanic contractions have been assessed in soleus muscles isolated from guniea-pigs which had been maintained on food with or without terbutaline for 5 days. 2 Terbutaline and adrenaline increased cyclic AMP content and suppressed subtetanic contractions, and regression analysis indicates a statistically significant correlation between these two effects (P less than 0.01). 3 In muscles obtained from terbutaline-treated animals, the effects of terbutaline and adrenaline on cyclic AMP content, active Na-K-transport and subtetanic contractions were all considerably suppressed, but insulin stimulated 22Na-efflux and affected subtetanic contractions to the same extent as in the muscles obtained from the control group. 4 The results suggest that terbutaline treatment leads to a reduction in the number of beta 2-adrenoceptors in skeletal muscle or an impairment of their function. 5 The results provide further support for the idea that the effect of adrenaline or insulin on skeletal muscle contractions is the outcome of stimulation of active Na-K-transport.
D000818:Animals; D000242:Cyclic AMP / Q000378:metabolism; D004837:Epinephrine / Q000494:pharmacology; D006168:Guinea Pigs; D066298:In Vitro Techniques; D007328:Insulin / Q000494:pharmacology; D009119:Muscle Contraction / Q000187:drug effects*; D009132:Muscles / Q000187:drug effects* / Q000378:metabolism; D011188:Potassium / Q000378:metabolism; D011941:Receptors, Adrenergic / Q000187:drug effects*; D011943:Receptors, Adrenergic, beta / Q000187:drug effects*; D012964:Sodium / Q000378:metabolism; D013726:Terbutaline / Q000494:pharmacology*
D007328:Insulin; D011941:Receptors, Adrenergic; D011943:Receptors, Adrenergic, beta; D012964:Sodium; D000242:Cyclic AMP; D013726:Terbutaline; D011188:Potassium; D004837:Epinephrine