Morphological studies on the synthesis of secretory granules in convoluted tubules of mouse submandibular gland.

The synthesis of zymogen-like secretory granules in convoluted tubules of mouse submandibular gland (SMG) was investigated by histometry, light microscopy and electron microscopy. In normal males secretory granules in the SMG increased greatly from 25 days after birth and reached a maximum level 50 days after birth. Castration of adult male mice markedly decreased the level, but it was completely restored by testosterone administration. A parallel was found between change in the granule level and the amount of rough endoplasmic reticulum (RER) in the convoluted tubular cells during development or after various treatments. Development of the Golgi apparatus was also observed in the cells when the granules increase. Both the increase in the granules and in the RER induced by testosterone were prevented by actinomycin D or puromycin. These results indicate that the granule contents are synthesized on the RER under the control of testosterone, and then condensed in the Golgi apparatus.