Chemical protection against life shortening and causes of death after a single or fractionated whole-body exposure of mice to ionizing radiation

The causes of death and the effect of radioprotection were studied in BALB/c and C57B1 mice exposed to a single dose of X-rays. The causes of death were classified among 12 different diseases and evaluated for competing risks. The life-shortening effect in BALB/c mice depends linearly on the dose, and dose-reduction factors of 1.3 for AET and 2.1 for a protector mixture are obtained. Radiation-induced life shortening is caused by an induction of specific diseases, mainly thymic lymphoma, myeloid leukaemia, glomerulosclerosis and non-cancerous lung lesions. The frequency of lung carcinoma in BALB/c mice decreases after X-ray of more than 350 R but is latency period shortens. In BALB/c mice protection is most effective against thymic lymphoma, but is also discernible for myeloid leukaemia and glomerulosclerosis. The protection in C57B1 mice resembles that in the BALB/c strain. Thus, protection is effective against thymic lymphoma (also against liver adenomas, all carcinomas and myeloid leukaemia) as well as against glomerulosclerosis). In another experimental series, mice were subjected to fractionated irradiation at various doses and time intervals until death. Controls and AET-protected mice die when an accumulated dose of about 2 kR is attained; mixture-protected mice can sustain up to 4 kR almost independently of the size and interval of fractions when one corrects for acute lethality. Death is caused by bone marrow failure after short times, and by fibrosis at later periods. (author)