title: Epinephrine potentiates adenosine-stimulating effect on glucagon secretion.
abstract: The aim of the present work is to investigate a possible interaction on glucagon secretion between adenosine, a compound released by tissues in energy-deficient states, and epinephrine, the hormone of stress largely implicated in such conditions. The study was performed using the isolated perfused rat pancreas in presence of a physiological glucose concentration (5 mM). Epinephrine administered at a low concentration (0.01 microM) was ineffective on glucagon secretion, and adenosine at 1.65 microM was previously shown to be moderately stimulating. This nucleoside alone induced a transient increase of glucagon secretion rate that peaked at 300% of basal value at 2 min; in presence of epinephrine (ineffective per se) the rise induced by the nucleoside alone was doubled. This potentiating effect was not observed with the neurotransmitter norepinephrine at the dose tested. Propranolol (1 microM) did not alter the potentiating effect of epinephrine but this effect was completely suppressed by the alpha-blocker, phenoxybenzamine (6 microM). In conclusion epinephrine potentiates an adenosine-stimulating effect on glucagon secretion; this effect seems more specific for the adrenal medulla hormone epinephrine, since norepinephrine at the same dose is ineffective; it is mediated via alpha-adrenergic receptors. It is attractive to speculate that epinephrine and adenosine act in potentiating synergism on glucagon secretion; this might be of physiological importance during stressful energy-deficient situations.
mesh_terms: D000241:Adenosine / Q000494:pharmacology*; D000818:Animals; D004357:Drug Synergism; D004837:Epinephrine / Q000494:pharmacology*; D005934:Glucagon / Q000378:metabolism*; D008297:Male; D009638:Norepinephrine / Q000494:pharmacology; D010643:Phenoxybenzamine / Q000494:pharmacology; D011433:Propranolol / Q000494:pharmacology; D051381:Rats; D011942:Receptors, Adrenergic, alpha / Q000187:drug effects; D011943:Receptors, Adrenergic, beta / Q000187:drug effects; D012636:Secretory Rate / Q000187:drug effects
chemical_list: D011942:Receptors, Adrenergic, alpha; D011943:Receptors, Adrenergic, beta; D010643:Phenoxybenzamine; D005934:Glucagon; D011433:Propranolol; D000241:Adenosine; D009638:Norepinephrine; D004837:Epinephrine