Morphofunctional study of rat pleural mesothelial cells exposed to low frequency noise

Background: Vibroacoustic disease (VAD) is a noise-induced pathology occurr ing in workers occupationally exposed to large pressure amplitude (greater than or equal to 90 dB SPL) and low frequency (less than or equal to 500 Hz ) (LPALF) noise, over long periods of time (greater than or equal to 10 yr) . Patient complaints frequently involve the respiratory tract. There have b een three cases of pleural effusion of unknown etiology and with unusually long recovery times. To better understand what may be occurring we studied the effects of LPALF noise on the morphological and functional characterist ics of pleural mesothelial cells of Wistar rats. Methods: The animals were exposed to LPALF noise for periods ranging from 24-600 h. An intrapleural i nstillation of calcium tungstate was performed, and after sacrifice the ple ural visceral and parietal leaflets were studied by scanning electron micro scopy. Results: Acute exposure to LPALF noise caused a temporary decrease i n the number of mesothelial microvilli, and prolonged exposure resulted in a definite decrease in their number as well as an impairment of their capac ity to absorb particles within in the pleural space. Conclusion: These resu lts explain the pleural pathology found in human patients with VAD and conf irm the deleterious effect of LPALF noise on the respiratory system.