Effect of X-radiation on Salivary Gland Growth in the Rat

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Abstract
The effect of x-radiation confined to tissues of the head and neck of female rats, on post-natal growth and development of the major salivary (submandibular and parotid) and external orbital (lachrymal) glands has been studied by determining allometric changes in gland weight, and by histometric measurements made in the submandibular gland. Single doses of x-rays, 200–1600 rads, caused dose-dependent reductions in glandular growth rates similar in magnitude for the three organs: in the submandibular gland this was shown to be primarily related to parallel dose-dependent effects on cell proliferation. Auxetic growth (cell enlargement and hypertrophy) and various specific types of cell differentiation occurring in these tissues during their development were radio-resistant, and were shown to be compensatory mechanisms which counteracted effects of irradiation on proliferative growth, considerable restoration of submandibular gland weight with preservation of acinar/duct ratios resulting from auxetic growth of acinar cells. In irradiated submandibular and external orbital glands, acinar cell hypertrophy was associated with nuclear enlargement and hyperchromaticism, which is considered to represent polyploidization. The irradiated parotid showed no such nuclear or cell enlargment and greater atrophy, particularly after lower doses. The definition of sexual dimorphism of the submandibular gland in the rat is discussed. No evidence was obtained that local irradiation caused a ‘masculinization’ of these tissues.