Effects of raw soy diet on the rat parotid gland

Soy is increasingly used as a food additive. In women, it is recommended as an alternative to hormonal replacement therapy and/or a preventive agent against breast cancer and osteoporosis. Previous data revealed that rats fed on raw soybean diet developed pancreas hypertrophy and hyperplasia. An animal model was used in our experiment to examine the effects of raw soybean on parotid gland of rats. The purpose of this study was to light on the role of different neuropeptide-containing nerve fibres on changes in the acinar cells. The morphological structure and the neuropeptide-containing nerve fibers (NPY, GAL, SOM, SP, CGRP, VIP) of the glands were examined by light and electronmicroscopy. Significant increase of the organ weight was detected in the animals fed by raw soybean compared to control samples. Changes in the number of different neuropeptide-containing nerve fibres were various: Significant decrease in the NPY-immunoreactive (IR) and significant increase in the GAL-IR nerve fibres were observed. Slight but not significant increase in VIP-IR; and no changes in the other IR nerve fibres were found. The electronmicroscopic alterations of acinar cells were manifest, where a large number of undifferentiated glandular cells were seen among the acini. Some of these cells contained two nuclei and their cytoplasm contained only a few secretory granules. These granules were similar to those in the mucous cells but not to the serous ones. The results presented here provide direct morphological evidence for the role of raw soy on the density of different neuropeptide-containing nerve fibres inducing proliferation in the acinar cells of parotid glands from rats. It is suggested that the hypertrophic changes in the glands might be caused by the alterations of nerve fibres.