The aim of the presented study was to observe acute and subacute discrete TGF-beta1 production after a low-dose whole-body radiation stimulus, known to induce thrombocytopenia. TGF-beta1 mRNA production and the number of thrombocytes was followed up in two mouse strains with different tendencies to the origination of fibroses. Mice of the C57BL/6 and C3H/J strains were exposed to a whole-body dose of 7 Gy. Non-irradiated mice of both strains were used as negative controls. The relative number of thrombocytes recorded in lung capillaries was significantly lower in both strains on day 9 after irradiation in comparison with controls. This finding was in accordance with a decrease in the number of thrombocytes in the peripheral blood in irradiated animals of both strains. On day 56 relative platelet counts reached physiological numbers in comparison to controls. On the other hand, TGF-beta1 mRNA production was higher in the C57BL/6 strain (on day 9) contrary to minimal production in the C3H/J strain (on day 9) or no production in both groups on day 56 and in controls. Thus, TGF-beta1 production without increased thrombocyte trapping in lung vessels in acute stage suggests that an additional mechanism is involved in low-dose radiation-induced cytokine synthesis in lung tissue besides the release of growth factors from thrombocytes.

Institute of Biophysics 1st Medical Faculty Charles University Prague Czech Republic

Cytokines and radiation-induced pulmonary injuries