Ultrastructural studies on the bleb formation in seal and rat submandibular gland striated ducts.

For the present study Seal (Phoca vitulina) and rat submandibular gland striated ducts were investigated by electron microscopy. Both normal and stimulated animals (starved for 24 h and then fed 2 h before the tissues were removed) were examined. Basal invaginations of the cell membrane with areas heavily loaded with mitochondria were typical features of both animals. Secretory granules were especially numerous in the apical part of stimulated duct cells. The granules were separated from the luminal membrane of the cells by a condensed area called the spearating zone. Apical protrusions or blebs, which were frequently occurring in striated ducts of both animals, are interpreted as manifestations of apocrine secretion. It was concluded that this way of apocrine secretion is a fundamental function, since seals, which have salivary glands of a rather simple composition with acini which are functionally reduced, have retained the ability to form blebs.