Relative biological effectiveness of tritiated water on cultured mammalian cells at molecular and cellular level

Factors that affect RBE values have been investigated in cultured cells. It was shown that: (1) Different RBE values were obtained with the same tritiated water treated cells depending upon the biological end-point; this may be related to target size. (2) The RBE value for one end-point (e.g. cell killing) in different cell types was often different. In some cells, the RBE value increased with reducing dose; in other cells, the value remained constant. (3) The RBE value for tritiated water seemed to fit a general RBE-LET relationship. These results suggest that although the RBE value might vary from 1 to 2 when cells are exposed to HTO, there are situations where the value becomes higher than 2; these are associated with low dose and low dose rate exposures in some cell types. (author)