Effects of head and neck radiotherapy on major salivary glands--animal studies and human implications

Abstract

Objective: The purpose of this review is to suggest an updated description of early and late irradiation effects on salivary glands in rodents. Based on this description, the mechanism of the underlying xerostomia will be discussed.

Study design: To examine the assumption that the so-called "irradiation" effects on the parotid gland of the rat during the first two weeks are actually mucositic effects and, thus, are transient, both function and partitution-coefficient parameters of the salivary glands were examined in both irradiated and pair-fed but not irradiated rats.

Materials and methods: Various studies were performed in which irradiated and non-irradiated rats were examined at varying intervals up to one year post-irradiation. Head and neck irradiation resulted not only in dysfunction and tissue loss of the salivary glands but also in a systemic effect expressed as profound body weight loss.

Results: Based on the literature available and on our own studies, we believe that one can suggest an overall mechanism for the damage induced by irradiation to the salivary glands. Our results have shown a mutual delayed expression of irradiation-induced damage in both parotid and submandibular, more evident in the parotid gland.

Conclusion: We have suggested the following mechanism for the parotid irradiation-induced specific damage: The injurious agents resulting in delayed serous cell death leading to the specific parotid radiosensitivity are transition, highly redox-active metal ions, such as Fe and Cu, associated with secretion granules.