Protein free diet feeding: Effects of the sympathetic activity and salivary evoked secretion in the submandibular gland of the rat

JUAN C. ELVERDIN; A.P CHIARENZA; M.A. LUCHELLI; MARCELO S. VATTA; LILIANA G. BIANCIOTTI; PATRICIA BOYER; MARIA I. VACAS

ARCHIVES OF ORAL BIOLOGY

Elsevier

Lugar: Amsterdam; Año: 2006 vol. 51 p. 621 - 628

0003-9969

Summary 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 a1-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 lowersSMG sympathetic and cholinergic activity leading to supersensitivity as revealed by up-regulation of a1-adrenergic receptor number and increased autonomic-evoked salivation.