The postnatal development of acini in the salivary glands of 2-42 day old rats was studied by Periodic acid-Schiff (PAS), Alcian blue (AB), AB-PAS, Aldehyde fuchsin (AF) and AB-AF histochemical staining method. In the submandibular acini, rudimentary secretory unit, designated as terminal tubule, was located at the end of duct system and consisted of three cell types ; PAS-positive acinar cells, PAS-negative proacinar cells and PAS-positive terminal tubule cells at 2 days of age. At 14 days of age, most cells of acini were PAS-positive, but negative for AB and AF staining. From 21 days of age, acinar cells differentiated into AB-positive cells. In the sublingual acini, most of mucous cells containing neutral and sulphated mucin showed positive reaction to PAS and AF at 2 days of age. With age, mucous cells that stained by
AB increased. Serous cells were negative to FAS, AB and AF at 2 days of age. Serous cells that stained by only PAS appeared at 28 days of age. In the parotid acini, terminal cell clusters were negative to PAS, AB and AF at 2 days of age. PAS positive acinar cells appeared from 7 days of age. At 28 days of age, the general morphology of acini appeared to be fully differentiated and showed almost similar histological architecture to that of the adults. These results suggest that postnatal development of salivary acinar cells has close relation to weaning time of the animal.
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