HISTOLOGICAL FINDINGS IN THE SALIVARY GLANDS OF THE RAT FOLLOWING SODIUM FLUORIDE ADMINISTRATION

¹ School of Dentistry, University of Washington, Seattle, Wash.

1. Two groups of rats were studied, each group consisting of ten experimental and five control animals. The two groups were designated as "acute" and "chronic," based on the duration of the experimental period and amount of sodium fluoride administered. The acute group animals received daily intraperitoneal injections of 2.5 per cent isotonic aqueous NaF solution for 15 days, while the chronic group experimental animals received lower volume injections of the same solution on alternate days over a 100-day period.

2. At autopsy, no significant changes were observed either in the gross appearance of the animals (incisor teeth excepted), or in the gross structure of the salivary glands.

3. The chief histological effects of sodium fluoride administration, confirmed in many instances by statistical analysis, were as follows:

Parotid Gland.—(1) Increased mitotic division of alveolar cells (chronic group experimental animals), (2) increased size of alveolar cell nuclei (chronic group experimental animals), (3) clear unstained areas and a lack of uniform staining in the alveolar cell cytoplasm, features suggestive of degenerative change. There were reasons for considering this a fatty degeneration, and (4) increased separation of alveoli and an apparent increase in the amount of intralobular connective tissue.

Submaxillary Gland.—(1) An increase in the number of Type 1 serous cell alveoli per unit area (chronic group experimentals. The Type 1 cell is described by Stormont36 as a cell containing large highly refractive granules, (2) a modification of serous cells of the second type (Type 2), including a change in their size and alveolar arrangement and their greater compression between alveoli of Type 1 cells, and (3) evidence of cytological change in Type 2 cells. Vacuolation and unusual staining of the cytoplasm and the enlarged, irregular shape of many cell nuclei pointed to degeneration, possibly of a fatty nature. These Type 2 cell changes were apparent, though to a lesser degree, in submaxillary glands of the acute experimental group.

Sublingual Gland.—Experiment tissues were devoid of change.

The effects of sodium fluoride absorption were such as to produce definite change in the structure of the parotid and submaxillary glands. Similar dosage of sodium fluoride did not influence the histological appearance of the sublingual gland.