, Volume 198, Issue 2, pp 363-371

The postnatal development of the submandibular gland of the mouse

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Summary

The postnatal development of the submandibular gland was investigated in male mice of the Swiss-Webster strain, which were killed at 1, 2, 3, 4, 5, 6, 8, 10, 12, 16 and 20 weeks of age, while the older mice had been weaned at 3 weeks of age. The mean weight of the submandibular gland increases from 9.5 mg at 1 week to 232.9 mg at 20 weeks of age, and the rate of increase is rapid between 3 and 10 weeks of age. The gland's contents of DNA, RNA and protein increase in a similar manner.

The changes in the constituent cell types of the gland were studied in radioautographs prepared from Epon-embedded sections of mice given 3H-thymidine and stained with toluidine blue. At 1 week of age, the gland consists of acinar cells (36%), intercalated duct cells (26%), juxta-acinar cells (13%), striated duct cells (12%) and others. The cellular composition of the gland changes little before weaning, but the absolute number of all types of cells increases with age. Between 3 and 4 weeks, juxta-acinar cells disappear and granular convoluted tubule cells appear and increase rapidly in number with age. The rapid expansion of the population size of granular convoluted tubule cells after weaning coincides with the second peak of increased proliferative activity of intercalated duct cells, whereas all the other cell types show a progressive decrease in their proliferative activity with age. In spite of the burst in proliferative activity, there is no corresponding increase in the absolute number of intercalated duct cells. The number of striated duct cells peak at 5 weeks of age and then declines. These findings indicate that the mitoses of intercalated duct cells give rise to granular convoluted tubule cells through a stage of striated duct cells. At 20 weeks of age, the gland consists of granular convoluted tubule cells (47%), acinar cells (28%), intercalated duct cells (12%), striated duct cells (1%) and others.

Supported by Public Health Service Research Grant AMDE 19753 from the National Institute of Health. The authors are indebted to Mr. I. Borcsanyi for technical assistance