Morphologic changes in the parotid gland induced by low frequency noise - An histology study

The goal of this study is to evaluate the morphological abnormalities of the parotid gland of the Wistar rat exposed to low frequency noise (LFN) (=500Hz, infrasound included). Long-term exposure to LFN, may lead to the development of vibroacoustic disease, a multisystemic disease, characterized, among other abnormalities, by a excessive proliferation of extracelular matrix. METHODS: We studied 50 parotid glands of mice exposed to LFN for 2184 consecutive hours. The sections were stained with HE and PAS. RESULTS: Multiple alterations were observed, namely, vacuolar degenerescency (PAS negative) in the absence of inflammatory signs. Hialinization of connective tissue, cellular death and lobular necrosis were also observed. Important vascular changes, mainly in small vessels, with thickening of the walls, was found. DISCUSSION: There are no previous studies of LFN concerning the parotid gland. We found diffuse fibrosis of the connective tissue. The vacuolar degenerescency that we observed is also found in other pathological situations, such as ethanolic fat degenerescency, in "necrotising syalometaplasy", or in cases of irradiation with X-rays. The mechanism of LFN-caused lesions is not, yet, determined.