Time scale of radiation damage by 2,4-dinitrophenyl-aziridine (CB 1954) in Chinese hamster cells: a rapid-mix study

A rapid-mix device was used to study the time-scale of radiation sensitization of hypoxic cells by CB 1954, a monofunctional alkylating agent. It has an electron affinity (E1(7)-385 mV) similar to that of misonidazole but its effectiveness as a sensitizer occurs at a five-fold lower concentration under stationary-state conditions. In the rapid-mix study, the enhancement ratio (e.r.) value of 1 mmol dm-3 CB 1954 rapidly rises to 1.75 within 120 ms, with no further rise by 500 ms. The e.r. obtained is lower than that observed under stationary-state conditions for a similar concentration. The data suggests that CB 1954 sensitizes by at least two independent mechanisms.