Rat adrenal medulla modular organization

Relevance. The concept of the tissue morpho-functional units (modules) of the adrenal medulla is currently not fully developed for adrenaline-storing (A-) cells and completely undeveloped for noradrenaline-storing (NA-) cells. Aim. Separately for A- and NA-cells, establish modules in adrenal medulla based on criteria developed by fundamental histology. Materials and Methods. The study used serial, semithin, and ultrathin sections of the adrenal glands, 7-9 µm thick, from 6 adult male Wistar rats (weight 335 ± 25 g). The sections were stained according to the Honoré method with additional staining with toluidine blue, which allows one to reliably distinguish between A and HA cells in the medulla. A cells are stained blue and HA cells are stained green. Light and electron microscopy was used to visualize serial, semithin, and ultrathin sections of the adrenal glands of adult male rats with A- and HA-cell differentiation. Results and Discussion. A-cells formed round clusters, in which they were located in one layer on the basement membrane. Their lateral sides closely adjoined each other, while the inner sides (the central part of the complexes) formed intercellular expansions, microprotrusions, and primary cilia. Less firmly pressed NA-cells formed polyhedral beams. Both types of cell complexes were associated with auxiliary components (stromal, nervous, circulatory, etc.). The central expansions of A-cell round clusters apparently to serve to retain some of the already produced adrenaline, which increases the readiness of the medulla to rapidly release large amounts of adrenaline in case of hyperacute stress. Accordingly, the adherence of A-cell complexes to a rounded shape is determined by the need to create such central isolated storage expansions. NA-cells are located more freely and do not form isolated intercellular expansions. This allows NA-cells to wedge between stably round A-cell complexes and form polyhedral beams as a result. Conclusion. It was found that the rat adrenal medulla contains two logically and morpho-functionally distinct types of specific modules. A-module are A-cells rounded cluster and NA-module is polyhedral NA-cells beam, both associated with auxiliary components.