RESPONSE OF RAT SALIVARY-GLANDS TO MASTICATION OF PELLETED VITAMIN-A-DEFICIENT DIET

Interpretation of previous studies of the effects of hypovitaminosis A on salivary glands is confounded by the atrophic effects of liquid or powdered diets. The purpose of this study was to re-evaluate the effe cts of vitamin A deficiency on the morphology and function of rat sali vary glands using a pelleted diet that promotes physiological levels o f masticatory stimulation. Profound vitamin A deficiency resulted in a marked decrease in stimulated parotid secretion. Histological evaluat ion demonstrated the development of squamous metaplasia in the ducts o f parotid, submandibular and sublingual salivary glands; however, atro phy was observed only in serous salivary glands. In the parotid gland the degree of atrophy corresponded to the decrease in stimulated secre tion. Mild hypovitaminosis A (before the development of squamous metap lasia in ducts) was associated with distinctly different effects. The parotid gland was moderately enlarged. There was also a significant in crease in stimulated secretion, which was not explained by changes in gland size, muscarinic receptor number or affinity, or receptor mediat ed calcium signalling. Copyright (C) 1996 Published by Elsevier Scienc e Ltd.