title: Adrenergic control of the glucagon response to ammonia in the perfused rat pancreas.
abstract: The isolated perfused rat pancreas was used to investigate how adrenergic influences within the pancreas might mediate ammonia-induced glucagon secretion. The addition of 2 mM ammonia to the perfusate increased norepinephrine release and glucagon secretion in the effluent. Upon cessation of ammonia addition, a pronounced burst of glucagon release was observed. Alpha-adrenergic blockade with phentolamine (10 microM) blocked the glucagon response to ammonia. Beta-adrenergic blockade with propranolol (10 microM) had no significant effect on the amount of glucagon release induced by ammonia. Depletion of norepinephrine from sympathetic nerve terminals by pretreatment with 6-hydroxydopamine lowered the pancreatic norepinephrine content to less than 16% of the control value and diminished the glucagon and norepinephrine response to ammonia almost completely. The burst of glucagon release after the removal of ammonia was inhibited to 2% of the control value by phentolamine and to 57% by propranolol. Pretreatment with 6-hydroxydopamine reduced the burst of glucagon secretion to 28% of the control value. Neither phentolamine nor propranolol reduced the magnitude of the ammonia-induced suppression of insulin secretion. We conclude that the effect of ammonia on glucagon release from the isolated rat pancreas is mediated by intrapancreatic adrenergic control.
authors.affiliation: Third Department of Internal Medicine, Ehime University School of Medicine, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Ichiba
authors.forename: A
authors.initials: A
authors.lastname: Tanaka
authors.forename: Y
authors.initials: Y
authors.lastname: Ohta
mesh_terms: D000641:Ammonia / Q000494:pharmacology*; D000818:Animals; D005934:Glucagon / Q000378:metabolism*; D006892:Hydroxydopamines / Q000494:pharmacology; D066298:In Vitro Techniques; D007515:Islets of Langerhans / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D009638:Norepinephrine / Q000378:metabolism*; D016627:Oxidopamine; D010477:Perfusion; D010646:Phentolamine / Q000494:pharmacology; D011433:Propranolol / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D012016:Reference Values
chemical_list: D006892:Hydroxydopamines; D000641:Ammonia; D016627:Oxidopamine; D005934:Glucagon; D011433:Propranolol; D009638:Norepinephrine; D010646:Phentolamine