In this paper

the preventive function of 6

7-dimethoxycoumarin for whole-body gamma-irradiated rats has been reported.

By giving ip 40—60 mg/kg to rats once 7—15 min before an exposure of 6—11 Gy

the percentage of survival of 30 days in haemopoitic type death was raised to 28.5%; the average protection coefficient was 1.940±0.8; DRF (dose reduce factor) was 1.149 for non-inbreed line rats; and the body

spleen and thymus weights were all increased. The antiradiation effect was found to be better when the drug was given (ip. or po.) 1/4—1 hour before an exposure. The variation of drug dosage (ip. 10—60 mg/kg) had little effect on the antiradiation function. The preventive effect of 6

7-dimethoxycoumarin seemed poor for rats with the gastrointestinal type acute radiation sickness.