Combined effect of space radiation and adjuvants on mice in vivo
Abstract
Recently we investigated the cytogenetic effects of low-dose-rate high-LET radiation on SHK mice in the radiation field behind the concrete shield of the Serpukhov accelerator with 70 GeV proton energy, that simulates the spectral and component composition of radiation fields formed in the conditions of high-altitude flights. It was found that low doses of high-LET irradiation led to an increase in the cytogenetic damage in mice which can be compared with level of spontaneous lesions. At the same time no decrease of cytogenetic damage was detected after irradiation with the challenging dose of 1.5 Gy, i. e., no adaptive response (AR) takes place in polychromatic erythrocytes (PCE) as opposed to low doses of chronic X-radiation. The goal of the present work was to determine if there is any influence of combined action of low doses of high-LET radiation and adjuvants on the cytogenetic damages and solid tumor growth in mice. Two-month-old SHK male mice were used. A search for potential adaptogens was performed among the adjuvants such as dibazol and calcium chloride. In each experiment, a group of animals was exposed to low doses of high-LET radiation and treated with dibazol or CaCl2 solutions after that mice were additionally irradiated with X-radiation according to the scheme of AR: 0.1 Gy + 1.5 Gy. After 28 h, the animals of all groups were killed by the cervical dislocation. Bone marrow specimens for calculating micronuclei (MN) in PCE were prepared by a conventional method with minor modifications. The influence of combined treatment of high-LET radiation and adjuvants on the growth of solid tumor of Ehrlich ascite carcinoma was estimated by measuring the size of the tumor at different times after the inoculation of ascitic cells into the femur. Our earlier study has shown that dibazol when used alone not only induced AR but also increased the magnitude of radiation AR when used in combination with low doses of X-radiation. In present work the obtained results indicate that, in contrast to X-radiation, the exposure of mice to the combined action of dibazol and the dose of 0.16 Gy (0.004 Gy/day) and 0.15 and 0.2 Gy (0.01 Gy/day) of high-LET radiation as well as high-LET radiation alone induced no AR and increased the tumor growth. The combined irradiation of mice with the dose of 0.2 and 0.3 Gy and calcium chloride did not induce the AR too. Moreover the mean size of the tumor of mice pretreated with the dose of 0.3 Gy (0.01 Gy/day) did not differ from those of unirradiated males, while irradiation of mice with this dose in the presence of calcium chloride increased the mean size of the tumor significantly as compared to unirradiated males. It is essential that treatment with all adapting agents led to the increased levels of cytogenetic damage as compared to the level of spontaneous lesions. The results of the study indicate that low doses of high-LET radiation have more serious genetic damages compared to low doses of chronic γ -radiation in the bone marrow cells. In addition the obtained data show that the complex use of adjuvants and such radiation under radiotherapy of tumor can promote the negative effect.
- Publication:
-
39th COSPAR Scientific Assembly
- Pub Date:
- July 2012
- Bibcode:
- 2012cosp...39.1861S