title: Protein free diet feeding: effects on sympathetic activity and salivary evoked secretion in the submandibular gland of the rat.
abstract: Protein restriction impairs the salivary flow rate and composition in human and rats. The aim of the present work was to establish the effect of low protein (casein 5%) and protein free (casein 0%) isocaloric diets on sympathetic activity and salivary evoked secretion in the submandibular gland (SMG) of the rat. After 21 days, rats fed casein 0% presented: (a) a significant shift to the left of the dose-response curves (DRC) to the autonomic agonists-norepinephrine (NE), methoxamine, isoproterenol (ISO) and methacholine; (b) increased food consumption (p<0.001); (c) decreased body (p<0.001) and SMG (p<0.001) weights maintaining SMG/body (w/w) relation; (d) enhanced submandibular alpha1-adrenoceptor number without changes in the apparent dissociation constant (Kd); (e) increased submandibular NE content (p<0.05) and phosphoinositoside hydrolysis (p<0.001); (f) decreased submandibular tyrosine hydroxylase activity (TH) (p<0.01). Casein 5% feeding increased food consumption (p<0.01) and reduced body weight (p<0.05). This protein restriction increased metacholine-evoked salivation, but it altered neither submandibular sympathetic activity nor sympathetic-induced salivary secretion as compared to the Control group (C) fed a similar diet containing 25.5% protein. Present results suggest that in the adult rat, a protein free diet during 21 days lowers SMG sympathetic and cholinergic activity leading to supersensitivity as revealed by up-regulation of alpha1-adrenergic receptor number and increased autonomic-evoked salivation.
authors.affiliation: Cátedra de Fisiología, Facultad de Odontología, Universidad de Buenos Aires, M.T. de Alvear 2142, 3(er) Piso A (CP1122), Buenos Aires, Argentina. jelverdin@hotmail.com
authors.forename: Juan C
authors.initials: JC
authors.lastname: Elverdin
authors.forename: A P
authors.initials: AP
authors.lastname: Chiarenza
authors.forename: M A
authors.initials: MA
authors.lastname: Luchelli
authors.forename: M
authors.initials: M
authors.lastname: Vatta
authors.forename: L G
authors.initials: LG
authors.lastname: Bianciotti
authors.forename: P
authors.initials: P
authors.lastname: Boyer
authors.forename: M I
authors.initials: MI
authors.lastname: Vacas
mesh_terms: D000316:Adrenergic alpha-Agonists / Q000494:pharmacology; D000318:Adrenergic beta-Agonists / Q000494:pharmacology; D000818:Animals; D015415:Biomarkers / Q000032:analysis; D002364:Caseins / Q000008:administration & dosage* / Q000378:metabolism; D018679:Cholinergic Agonists / Q000494:pharmacology; D018753:Diet, Protein-Restricted; D007545:Isoproterenol / Q000494:pharmacology; D008297:Male; D016210:Methacholine Chloride / Q000494:pharmacology; D008729:Methoxamine / Q000494:pharmacology; D023421:Models, Animal; D010716:Phosphatidylinositols / Q000378:metabolism; D011502:Protein-Energy Malnutrition / Q000378:metabolism*; D011897:Random Allocation; D051381:Rats; D017208:Rats, Wistar; D012472:Salivation / Q000187:drug effects*; D013363:Submandibular Gland / Q000187:drug effects / Q000378:metabolism*; D013564:Sympathetic Nervous System / Q000187:drug effects / Q000502:physiology*; D014446:Tyrosine 3-Monooxygenase / Q000032:analysis / Q000378:metabolism
chemical_list: D000316:Adrenergic alpha-Agonists; D000318:Adrenergic beta-Agonists; D015415:Biomarkers; D002364:Caseins; D018679:Cholinergic Agonists; D010716:Phosphatidylinositols; D016210:Methacholine Chloride; D014446:Tyrosine 3-Monooxygenase; D008729:Methoxamine; D007545:Isoproterenol