Abstract
The detailed mechanisms which can explain the inherent radiosensitivity of salivary glands remain to be elucidated. Although DNA is the most plausible critical target for the lethal effects of irradiation, interactions with other constituents, such as cell membrane and neuropeptides, have been suggested to cause important physiological changes. Moreover, mast cells seem to be closely linked to radiation-induced pneumonitis. Therefore, in the present study the effects of fractionated irradiation on salivary glands have been assessed with special regard to the appearance of mast cells and its correlation with damage to gland parenchyma. Sprague-Dawley strain rats were unilaterally irradiated to the head and neck with the salivary glands within the radiation field. The irradiation was delivered once daily for 5 days to a total dose of 20, 35 and 45 Gy. The contralateral parotid and submandibular glands served as intra-animal controls and parallel analysis of glands was performed 2, 4, 10 or 180 days following the last radiation treatment. Morphological analysis revealed no obvious changes up to 10 days after the irradiation. At 180 days a radiation dose-dependent loss of gland parenchyma was seen, especially with regard to serious acinar cells in parotid gland and acinar cells and serous CGT (convoluted granular tubule) cells in the submandibular gland. These changes displayed a close correlation with a concomitant dose-dependent enhanced density of mast cells and staining for hyaluronic acid. This cell population seems to conform with the features of the connective tissue mast cell type. The parotid seems to be more sensitive to irradiation than the submandibular gland. Thus, the present results further strengthen the role of and the potential interaction of mast cells with radiation-induced tissue injury and alterations in normal tissue integrity.
Highlights
In a substantial manner with the development of radiationinduced pneumonitis and pulmonary fibrosis (Franzen et al, 1989; Bjermer et al, 1990; Nilsson et al, 1990a,b; 1992) we found it of interest to evaluate the correlation of connective tissue response and especially mast cells with radiationinduced damage in salivary gland tissue
This increase correlated with dose-related damage in parotid as well as in submandibular gland tissue recorded as a reduction in acinar cell density and a concomitant fibrosis
The connective tissue marker hyaluronic acid was closely linked to the described alteration in the tissue reaction with enhanced staining 180 days following the period of irradiation
Summary
Fifty white albino female rats of the Sprague-Dawley strain were used. They were 8 weeks old, and weighed approximately 200 g. They were fed water and chow ad libitum and kept on a diurnal light schedule. Before the animals were used for the experiments outlined below they were fasted for 18 h, and used before noon to avoid diurnal variations
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