Electron Microscopic Study on the Postnatal Development of the Mouse Parathyroid Gland

The parathyroid glands of mice from neonatal to 18 months old were studied by electron microscopy. Most chief cells of the parathyroid gland of one-day-old mice contained a small number of cell organelles and a few secretory granules. In most chief cells of mice between the ages of 3 and 21 days, the cytoplasmic volume of the cell and the number of free ribosomes, mitochondria and secretory granules were increased with age. At 21 days, the Golgi apparatus and the granular endoplasmic reticulum were relatively well developed. Most chief cells of mice between the ages of 1 and 6 months contained numerous free ribosomes, abundant mitochondria, well-developed granular endoplasmic reticulum and Golgi apparatus, and many secretory granules. Relatively numerous secretory granules were observed near the plasma membrane. In most chief cells of mice between the ages of 8 and 18 months, free ribosomes, prosecretory granules and secretory granules were reduced in number with age. An increase of the tortuosity of plasma membranes was observed with each stage of development. The results are discussed in relation to the function of the parathyroid gland during postnatal development.