The Induction of Adenomas by the Irradiation of Salivary Glands of Rats

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Abstract
The effect of X rays in concentrated (2550 -4250 r in 4 - 11 days) and protracted doses (6800 r in 6 months) on the 3 major salivary glands in male, female, and castrated female rats were investigated with particular reference to acinar injury, compensatory hypertrophy of the duct system and induction of adenomas. Acinar damage was greatest in the sublingual, least in the parotid and intermediate in the submandibular and varied with the sex of the rats. Compensatory secretory activity in the intercalated ducts of the sub-lingual and the secretory tubules of the submandibular reached a maximum at 3400 r and was greatest in males for both glands and absent in the sublingual of castrated females. No compensatory secretory activity in the duct system of the parotid was seen. Adenomas appeared only in regions in which the acini had disappeared, were of acinar type in the sublingual and submandibular and formed by the proliferation of the intercalated ducts. In the parotid they were of tubular type and formed by dedifferentiated ducts. In the male sublingual the incidence of adenomas decreased with increasing dose; at 3400 r it was 100% for males, 80% for females and 0% for castrated females. In the submandibular of male rats a peak of compensatory hypertrophy of secretory tubules at intermediate dose levels coincided with a low incidence of adenomas. In the parotid adenomas occurred only after protracted doses of X rays. The total incidence of adenomas was 65% in the sublingual, 40% in the submandibular and 11% in the parotid and varied with the sex of the rats and the type of treatment.