title: Effects of epinephrine and norepinephrine on glucose release from chinook salmon (Oncorhynchus tshawytscha) liver incubated in vitro.
abstract: The effects of two catecholamines, epinephrine (EP) and norepinephrine (NE), on carbohydrate metabolism were studied by incubating chinook salmon liver in vitro. Basal release of glucose over the course of a 5-h incubation was 7.93 +/- 1.70 mumol/g dry weight. Both EP and NE (2 X 10(-7) M) stimulated glucose release rapidly during the first hour. After 5 h, EP and NE significantly increased glucose release over basal levels to 43.55 +/- 9.01 and 32.75 +/- 6.17 mumol/g dry weight, respectively. Epinephrine- and NE-stimulated glucose release was dose dependent, with a minimum effective dose of 10(-9) M. ED50 for both agents was approximately 2 X 10(-7) M; maximal stimulation occurred at 10(-5) M. No difference in potency between the two catecholamines was found. The effects of adrenergic agonists and antagonists were also studied. Alpha-agonists, methoxamine and phenylephrine, had no effect on glucose release. Isoproterenol, a beta-agonist, stimulated glucose release in a manner similar to EP. The beta-antagonist, propranolol, inhibited both catecholamine- and isoproterenol-stimulated glucose release. Alpha-antagonists (phentolamine, prazosin, and yohimbine) had no effect on either catecholamine- or isoproterenol-stimulated glucose release. Epinephrine and NE stimulate glycogen phosphorylase activity; propranolol inhibits catecholamine-stimulated phosphorylase activity. These results indicate that catecholamines stimulate glucose mobilization in salmon liver by promoting glycogenolysis mediated through beta-adrenergic receptors.
authors.affiliation: Department of Zoology, North Dakota State University, Fargo 58105.
authors.forename: M A
authors.initials: MA
authors.lastname: Sheridan
mesh_terms: D000316:Adrenergic alpha-Agonists / Q000494:pharmacology; D000818:Animals; D046508:Culture Techniques; D004837:Epinephrine / Q000502:physiology*; D005947:Glucose / Q000378:metabolism*; D007545:Isoproterenol / Q000494:pharmacology; D008099:Liver / Q000378:metabolism; D009638:Norepinephrine / Q000502:physiology*; D006005:Phosphorylases / Q000378:metabolism; D012474:Salmon / Q000502:physiology*
chemical_list: D000316:Adrenergic alpha-Agonists; D006005:Phosphorylases; D005947:Glucose; D007545:Isoproterenol; D009638:Norepinephrine; D004837:Epinephrine