SECRETORY CELLS OF SUBMAXILLARY GLAND IN PERINATAL PERIOD OF DEVELOPMENT IN RAT

Secretory cell differentiation in the submaxillary gland of the rat was investigated electron microscopically within the period of the 19th-22nd embryonic and the 1st-6th postnatal days. Within this period three types of secretory cells were identified which differed mainly in the morphological appearance of their secretory granules. In addition to the previously described cells of the terminal tubules and the glandular cells of the acini, we observed secretory cells with polymorphic granules, characterized by the presence of small osmiophilic bodies in the matrix of the granules, both after simple and double fixation. The chronological occurrence as well as the quantitative representation of these three types of secretory cells changes in the course of the period investigated. The cells of the terminal tubules are differentiated at the 19th embryonic day; the secretory cells with polymorphic granules by the 21st embryonic day; the glandular cells of the acini do not appear until after birth. It is presumed that the cells of the terminal tubules are precursors of the glandular cells of the acini and that the cells containing polymorphic granules represent an intermediate stage between them. © 1969 Springer-Verlag.