[The relationship between the cytogenetic action of thiophosphamide and the duration of human cell treatment].

The subject of the present investigation is the expositional curves of the effect of thiophosphamide (as a drug and chemically pure compound) on chromosomes of human leucocytes at concentrations of 20 and 30 mcg/ml. Thiophosphamide was shown to retain its mutagenic activity during the 8 hrs incubation in the medium under the temperature of 37 degrees C. The percent of aberrant cells and the number of chomosome breaks per 100 cells appeared to show non-linear dependence on the exposition at different concentrations of thiophosphamide. The percent of aberrant cells as a function of the exposition of the mutagen can be satisfactorily described by the equation rho=-a exp [-Kt], where rho is a portion of aberrant cells, a and K are the coefficients, t is the time of the exposition of cells to the mutagen. But this equation results in a negative value of a number of aberrant cells in the control. No satisfactory description of the change in the number of chromosome breaks was found. The portion of chromatid breaks did not change under any exposition and remained at the level of 80%. The proportion of symmetric and asymmetric, complete and incomplete exchanges under different expositions with thiophosphamide did not change and did not differ from 1:1. Isoeffective points for different expositions to and concentrations of thiophosphamide were not obtained, this suggests a non-additive relationship between concentrations and expositions to thiophosphamide.