Regenerative effects of tetrachlorodecaoxide in BD IX rats after total-body gamma irradiation.

Tetrachlorodecaoxide (TCDO) was tested for its effects in BD IX rats when combined with a single dose nearing LD50 of total-body irradiation (gamma rays, 60Co). In pilot tests we found that TCDO administrations prior to or immediately after irradiation led to a very high mortality rate (up to 90%), whereas the initiation of TCDO treatment on Day 2, 3, or 4 after irradiation lowered the death rate noticeably, with optimum results when TCDO application was started on Day 4. In our major experiment on 100 BD IX rats, it was demonstrated that the following treatment schedule considerably decreased the death rate (from 44 to 4%): 15.5 mumol TCDO/kg body wt/day on Days 4-6 after irradiation and 7.75 mumol/kg body wt/day on Days 7-11. The animals treated with TCDO showed only mild anemia in the peripheral blood, accompanied by reticulocytosis and low-grade leukocytopenia. Examination of the bone marrow on Day 12 after irradiation revealed X-ray-induced agranulocytosis in the animals that had received only physiological saline solution, whereas in the bone marrow of the animals treated with TCDO there was erythropoiesis as well as myelopoiesis. In addition, the degree of hair loss and depigmentation occurring about 1 month after irradiation was considerably reduced by TCDO. From these results it can be postulated that TCDO has two different effects: as an oxygen donator it causes radiosensitization in the tissue when given before or immediately after irradiation; as an agent stimulating phagocytes and tissue regeneration, it promotes regeneration very effectively when damage is already evident in the tissue.