Alpha-adrenoceptor blockade by phentolamine inhibits beta-adrenergically and cholinergically induced glucagon secretion in the mouse.
Glucagon secretion is known to be stimulated by activation of the alpha-adrenoceptors. In this study, we investigated whether alpha-adrenoceptor blockade by phentolamine affects basal and stimulated glucagon secretion in the mouse. Phentolamine was injected intraperitoneally to mice at dose levels varying from 2.6 to 260 mumol/kg. It was found that, while decreasing plasma glucose levels, phentolamine did not over this wide dose range affect basal glucagon concentrations indicating an inhibition of the hypoglycaemia-induced glucagon secretion. Further, phentolamine clearly inhibited the glucagon secretory response to beta-adrenergic or cholinergic stimulation. Thus, phentolamine (2.6 mumol/kg), impaired the glucagon secretory response to the beta 2-adrenoceptor agonist terbutaline by 51% (P less than 0.01), and to the cholinergic agonist carbachol by 44% (P less than 0.02). We conclude that alpha-adrenoceptor blockade by phentolamine inhibits the glucagon secretion following hypoglycaemia or stimulation by beta-adrenergic and cholinergic agonists. Thus, the alpha-adrenoceptors seem to be of great importance for glucagon secretion in the mouse.
D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology*; D000818:Animals; D002217:Carbachol / Q000494:pharmacology; D005260:Female; D005934:Glucagon / Q000378:metabolism*; D051379:Mice; D010646:Phentolamine / Q000494:pharmacology*; D011943:Receptors, Adrenergic, beta / Q000187:drug effects / Q000502:physiology*; D013726:Terbutaline / Q000494:pharmacology
D000317:Adrenergic alpha-Antagonists; D011943:Receptors, Adrenergic, beta; D002217:Carbachol; D005934:Glucagon; D013726:Terbutaline; D010646:Phentolamine