Approximately 0.071% of an IV injected dose of226 Ra was initially retained in each eye of beagles and principally in the melanin granules of pigmented cells and the rodlike organelles of the tapetum. The retention half-times varied inversely with the injected dose, ranging from 105 days at 9.18 μCi/kg to 619 days 0.0593 μCi/kg. The resulting radiation-induced eye lesions were characterized by loss of pigment at the higher doses and melanosis and intraocular melanoma formation in the lower levels. Most of the eye melanomas arose in the ciliary body and tentatively appeared to be derivatives of the pigment epithelial layer. They occurred below the lowest osteosarcoma induction doses for226 Ra and228 Ra by factors of 3 and 8, respectively.

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