Morphological Changes in Thymus of Rats Following Whole-Body Exposure to Massive Doses of Radiation.

Abstract

More thymic tissue was present in young rats after exposure to over 10,000 r of X-ray than in comparable animals which had received lesser dosages. It was observed that the weight loss and degree of cytological alteration in the thymuses of rats were less after whole-body exposure to quantities of gamma or X-radiation above 10,000 r than after exposure to smaller dosages. Administration of 10,000 to 30,000 r of localized radiation to the thymic region or to the body with the head shielded, was regularly followed by significantly greater cellular destruction and weight loss in the thymus than after whole-body exposure to the same dose. Whole-body re-exposure to a massive dose of radiation within 1 hour after an initial total-body exposure to a small dose was regularly followed by less thymic weight loss and cellular destruction than after total-body exposure to the small dose alone. Findings show that exposure of the head during massive whole-body irradiation markedly influences the cellular response in the thymus.