Respiratory epithelia in Wistar rats.

Morphofunctional changes of respiratory epithelia became the object of intense study in Wistar rats after previous research showed that occupationally-simulated exposure to low frequency noise (500 Hz, including infrasound) induced irreversible lesions in these tissues. Aspects of normal respiratory epithelia in rats are lacking in the literature, and are the object of this report. Ten Wistar rats were kept in silence, fed standard rat food, and had unrestrained access to water (treated in accordance with 86/609/CE). The animals were sacrificed at 3.5 months of age, and respiratory epithelial fragments were excised and prepared for scanning (SEM) and transmission (TEM) electron microscopy. Brush cells (BC) were frequently observed with TEM, but with SEM they were often covered by the cilia of neighbouring cells. BC were always observed at the center of a ring of secretory cells (SC), in a rosetta-shaped formation. In TEM, the microvilli of SC surrounding the BC were uniform, and had the same density and shape in all cells. Multivesicular bodies were identified in areas within the BC. Formation and budding of vesicles from ciliary plasma membranes and from BC microvilli were frequently observed in both TEM and SEM. These data contribute to the understanding of the BC function.