DOSE-RATE EFFECTS ON ADAPTIVE RESPONSE INDUCED BY TRITIATED-WATER IN HUMAN BLOOD-LYMPHOCYTES

The present study examined the question whether adaptive response conc erning micronucleus induction in lymphocytes can be elicited by low-le vel pre-irradiation from tritiated water and can be influenced by the modification of the dose rate. Lymphocytes previously exposed in vitro to (HOH)-H-3 (0.2 - 6.6 MBq/ml) and subsequently irradiated with 1 Gy gamma-rays showed micronuclei frequency significantly lower than the sum of the yield induced by (HOH)-H-3 and gamma-rays separately. The d egree of the radioresistance induced by HTO pre-treatments became high er with decreasing dose-rate for a rather similar total adapting dose. The yield of observed micronuclei decreased until 40%-45% of the expe cted number. This limit is already reached at dose rate of 0.05 cGy/h.