Light microscopical and histochemical studies on developing rat parotid gland in prenatal, postnatal and adult terms

This research comparatively studied developmental distributions of the parotid gland in rats at intrauterine 17 days (prenatal term), 30 days (postnatal term), and 6 months old (mature stage), using routine histochemical and histological staining methods. It was observed at prenatal term that the connective tissue extensively occupied the gland area, including small nests of secretory cells and excretory duct patterns. Thus, progenitor secretory cells were found to be in smaller numbers at prenatal term as compared to those of the corpus glandule at postnatal and mature terms. At light microscopic observation through using Periodic Acid Schiff-PAS staining, PAS positive presecretory cells were occasionally visible, with dark pink cytoplasm. At postnatal term, the cells constituting the corpus glandulae were PAS negative. Although the cells in the secretory duct displayed a weak PAS positive reaction, the cells in pars striata were strongly PAS positive, as seen with strong granules. At mature stage, the corpus glandule rarely displayed PAS positive reaction. With Alcian blue, certain cells in corpus glandule displayed positive reaction at prenatal term, but these cells in the other terms displayed negative reactions. Abundant mast cells were present in the connective tissue in all the three stages. Plasma cells were observed primarily around the striated ducts in the postnatal and adult stages.