The lung parenchyma in low frequency noise exposed Wistar rats

Previous studies of low frequency noise (LFN) ( pound 500 Hz, including infrasound) exposed Wistar rat trachea and lung show that LFN induces irreversible lesions in the rodent respiratory system. Most notable was the behavior of the tracheal brush cell (BC) where fused microvilli were frequently captured in scanning electron microscopy. This study focuses on the alvoelar BC in LFN-exposed and control rat populations. Ten Wistar rats were exposed to 2160 hours of continuous LFN, then kept 1 week in silence before sacrifice. Another 10, age-matched rats were kept in continuous silence. All were fed standard rat food, and had unrestrained access to water (treated in accordance with 86/609/CE). Lung parenchyma fragments were excised and processed for scanning electron microscopy. In the non-exposed, alveolar walls were thin, and wall structure was well defined. In the LFN-exposed, walls were thickened and wall structure was almost effaced. Macrophages were found in the non-exposed specimens, but were not so frequent in the LFN-exposed. Both vein and artery walls were thickened. In the parenchyma of the exposed rats, an increase in type II pneumocytes was observed, and their microvilli were dramatically altered in terms of cell-surface distribution, sprouting direction, and amount. Unidentified black holes eruptin from the cell surface were observed. In the alveoli, 2 different types of BC's were observed: external and interstitial. In the exposed rats, microvilli of both types of BC were fused. These results confirm that LFN exposure can impinge on the entire respiratory system of living organisms.