The effect of pregnancy on the submandibular glands of mice

Structural changes occurring in the submandibular glands of mice during pregnancy were studied. The submandibular glands of 12 mice were examined immediately post‐partum, and those of a further 12 six weeks post‐partum. They were compared with glands of virgin female and young adult male mice. The mean weight of the glands immediately after pregnancy was 75% greater than that of the glands of virgin female mice of the same age. In both hematoxylin and eosin, and Mallory‐Heidenhain stained sections there was evidence of masculinization of the submandibular glands during pregnancy. The percentage of convoluted granular tubules in the glands increased; as did also the diameter of the tubules. The characteristic appearance of the constituent cells of the tubules in the gland of the virgin female, with basal striations and centrally located nuclei was converted to that seen typically in the young adult male, where the cells have basally located nuclei, and an abundance of apical granules but no basal striations. Regression in both the weight and microscopical appearance of the glands to the non‐pregnant condition occurred within the six weeks following pregnancy. The apparent masculinization of the submandibular glands during pregnancy is thought to be an expression of the complementary endocrine factors acting at that time.