Interaction of irradiation and BCNU in intestinal crypt cells

Survival of intestinal crypt cells was used to evaluate radiation and BCNU injury in LAF1 mice. A dose of 25 mg/kg reduced the crypt cell survival to 35% of irradiated control levels, if BCNU was given 3 hr post-irradiation. Drug was more effective when given pre-irradiation from -18 to -2 hr than post-irradiation (1210 rad) from 3 to 48 hr. When a radiation survival curve was determined 2 hr after the MTD dose, the slope was similar to controls, but a shift was caused by cell kill. When BCNU was given 2 hr before a 3 hr split-radiation, the survival ratio was 4 to 7 which was comparable to the control values. Although BCNU appears to enhance radiation cell kill when given before radiation, it does not appear to inhibit the repair of radiation-induced damage. Irradiation may alter the repair mechanism of cells damaged by BCNU