In utero and postnatal exposure of Wistar rats to low frequency/high intensity noise depletes the tracheal epithelium of ciliated cells.

Chronic exposure of men or rodents to low frequency/high intensity (LFHI) noise causes a number of systemic changes that make up the so-called vibroacoustic disease (VAD), a disorder that includes alterations of the respiratory system, namely, of its epithelial layer. We have investigated here the susceptibility of the tracheal epithelium of Wistar rats to in utero and postnatal exposure to LFHI noise by comparing its ultrastructure with that of the tracheal epithelium of control rats and of animals exposed to LFHI noise only after reaching adulthood (8 weeks of age). Scanning electron microscopy (SEM) of the inner surface of rat trachea was used to determine the relative areas covered by ciliated and non-ciliated cells. In rats that were exposed in utero and postnatally to LFHI noise, we observed that out of 100 microm(2) of tracheal epithelium only 31 +/- 14 microm(2) were covered by cilia, whereas in control rats; ciliated cells occupied an average of 60 +/- 18 microm(2) out of 100 microm(2) of the epithelium; this difference between the two groups was statistically significant (p <0.05). In rats that were exposed to LFHI noise only after reaching adulthood, cilia covered 55 +/- 22 microm(2) out of 100 microm(2) of the luminal surface of the trachea, a value that, although lower than that of controls, was not found to be statistically different. We conclude that (1) the tracheal ciliated cells are damaged by exposure of rats to LFHI noise if the animals are kept under this environmental aggression during in utero and postnatal periods; (2) tracheal ciliated cells from adult rats are more resistant to the deleterious effects of LFHI noise than pleura or lung alveolar cells that were shown before to undergo marked changes upon chronic exposure of rats to LFHI noise. These findings suggest a note of caution regarding pregnant women and young children: they should be prevented from areas where LFHI noise occurs, namely, in aircraft and textile industries where this type of environmental hazard is often present.