[Study on the radiation effects toward function and vessels of parotid gland in rat]

The effect of irradiation on the parotid gland was determined from 99mTc-pertechnetate (99mTcO4-) uptake and the course of vessels in the parotid gland, by investigating the uptake and excretion of 99mTcO4- in 60Co-gamma ray-irradiated rat parotid gland and ovserving the course of blood vessels and the histological changes. 1. In the uptake test, radiation activity of 99mTcO4- taken into the parotid gland per unit weight was the highest three days after irradiation for both 10 Gy (1.68 x 10(5)cpm/g) and 50 Gy (2.05 x 10(5)cpm/g); however, it began to decrease gradually at 7 days after irradiation. 2. In the clearance test, as in the uptake test, the radiation activity of 99mTcO4- per unit weight remaining in the parotid gland after stimulation of secretion, was high at 3 days after irradiation for both 10 Gy and 50 Gy (0.86 x 10(5), 1.28 x 10(5)cpm/g, respectively) and 7 days (0.88 x 10(5), 1.29 x 10(5)cpm/g) after irradiation, and gradually decreasing thereafter. 3. Stimulation-secretion coefficients determined from the ratio of uptake and clearance of 99mTcO4- were lower in all groups with irradiation than in the group without irradiation, with especially low values at 7 and 14 days after radiation. Thus, parotid function declined after irradiation. 4. With respect to the effect of irradiation on blood vessels, mild dilation was observed at 10 Gy at 3 and 7 days after irradiation, then constriction and meandering were noticed. Such changes were greater at 50 Gy than at 10 Gy. 5. Histological changes appeared 6h after irradiation in the 10 Gy- and 50 Gy-irradiation groups. Derangement of cells in the terminal parts, dilation of conduits, and proliferation of connective tissue were observed from 3 days after irradiation. 6. The periodic aid-Schiff (PAS) reaction was decreased in the 10 Gy- and 50 Gy-irradiation groups, with few PAS-positive cells at 28 days after irradiation. In conclusion, the decline in parotid function after 10 Gy- and 50 Gy-irradiation was related to histological changes in the vascular system and glandular tissues.