Ultrastructural and cytochemical studies of the subcommissural organ in the domestic chicken with special reference to the apical secretion.

Ultrastructural and cytochemical studies were undertaken with special reference to the apical secretion in the ependymal cells of the subcommissural organ in the domestic chicken. Glucose-6-phosphatase (G6Pase) and acid phosphatase (AcPae) were used as cytochemical markers for the endoplasmic reticulum (ER) and lysosomes, respectively. Periodic acid-thiocarbohydrazide-silver proteinate (PA-TCH-SP) cytochemistry was employed to detect glycoconjugates. Most dense bodies were negative with AcPase staining. Dilated cisternal of ER were reacted with G6Pase cytochemistry. Golgi saccules and several kinds of spherical bodies were stained with PA-TCH-SP cytochemistry. Our results suggest that: 1) most dense bodies in the apical cytoplasm belong to the secretory granules discharged into the ventricular cavity, 2) dilated cisternae of the ER serve as the storage site of the substance which eventually becomes the secretory product, however, contents of the ER are not directly released into the ventricular cavity. Findings of this studies lead us to speculate that there are two intracellular transportation via different compartments: one is a transport via small vesicles from the perinuclear ER to the Golgi apparatus and the other is a transport bypassing the Golgi apparatus via cisternae of ER from the perinuclear ER to the supra-Golgi region. The substances in these two structures seem to be intermingled with each other and matured into secretory granules. This granules may be discharged into the ventricular cavity by exocytosis.