Myeloid leukaemia and Harderian gland tumours in mice after X-ray and neutron exposure

Purpose: To determine dose effect relationships for myeloid leukemia and Harderian gland tumors .

Status: 1989 - 1992, X-rays terminated

Treatment: Single exposure to 250 kVp X-rays (126 mGy/min, 1.5 mm HVL)

Dosimetry: Twin ionization chamber ENDIP

Endpoints: Life-span study (spontaneous death) with macroscopic/microscopic pathology

Animal: Male CBA/H/Cne mice aged 3 months

Results: Harderian glands transplanted into the fat pad of isogenic recipients were used to quantitatively study cell survival and malignant transformation after X-ray exposure. The in vivo survival curve of the gland cells yielded a Do of 1.83 Gy and an extrapolation number of 7.23. The dose response for cell transplantation in vivo was compared with that for lesions in glands irradiated in situ. A high incidence of epithelial hyperplasia with severe dysplasia was observed in transplantation nodules after X-irradiation. The rate of gland tumors was significantly increased in whole-body-irradiated animals with a maximum incidence after 3 Gy. The risk of transformation per surviving cell was estimated for both dysplastic lesions and tumors. These results approximated a dose-squared relationship in both cases, suggesting a common induction mechanism at the cellular level. Myeloid leukemia was observed at all doses in whole body irradiated mice, and the maximum tumor incidence was reached at doses around 3 Gy.