Ultrastructural changes of secretory cells of salamander lingual salivary glands under varying conditions.

BACKGROUND

In general the ultrastructure of secretory cells can be modified under secretory stimulated and non-stimulated conditions. The ultrastructure of the lingual salivary glands of hibernating salamanders in the natural environment was examined and compared to those of fasted and fed animals kept in the laboratory.

METHODS

Hibernating salamanders of the species Hynobius tokyoensis were collected from the natural environment during the winter breeding season and sacrificed for this study. One group was sacrificed immediately, another group was kept under fasted condition, and another group was regularly fed; both of the latter groups were kept at room temperature for 1 month and then sacrificed. The tongue was fixed for electron microscopy and processed by conventional method, and semithin sections were histochemically examined for glycoconjugates.

RESULTS

The lingual salivary glands of this salamander species were composed of simple or often branched tubular glands opening onto the dorsal surface of the tongue. The secretory cells which composed their terminal portions were all columnar in morphology and histochemically mucous in nature. Under hibernation or prolonged fasting at room temperature, the mucous granules of these columnar secretory cells were decreased in number and the Golgi apparatus appeared inactive. A conspicuous structural peculiarity was multiple fingerprint-like structures of the rough-surfaced endoplasmic reticulum (RER). Most of these membranes were composed of stacks of tightly packed cisternae. Under regular feeding, the mucous granules were closely packed in the cytoplasm of the secretory cells and the basal nucleus was slightly enlarged. The Golgi apparatus showed progressive activation with distended saccules. The unique membranous arrangement of the RER which was observed in the fasting animals was completely absent, and the cisternae were irregular in width with considerable variation of the intercisternal spaces.

CONCLUSIONS

The tongue of the salamander H. tokyoensis has numerous tubular salivary glands which are mucous in nature. The architecture of the organelles in the secretory cells is subject to modification in response to the cellular metabolism.