Proliferative activity of lymphocyte cultures due to the mutagenic action of thiophosphamide in vivo and in vitro

: Thiophosphamide is capable of inhibiting the cell cycle after the treatment of rabbit blood lymphocytes in vivo and in vitro. To assess the proliferative activity of the cells during cultivation, use was made of the index of the mean division number which was experienced by the cells after mutagenic exposure prior to fixation. As the mutagen dose was raised in vivo and in vitro, the mean division number decreased linearly, namely by approximately the same value with an equivalent dose variation. This indicates that thiophosphamide produces the same cytotoxic action both in vivo and in vitro.