Effect of chemical protectors on the response of the intestine to roentgen or fission neutron irradiation.

The monosodium salt S-1-(2-hydroxy-3-amino) propylphosphorothioic acid (WR-77913) and S-2-amino ethylisothiuronium-Br-HBr (AET) were tested for protective effects against 4 MeV roentgen irradiation and fission neutrons in the mouse intestine. The parameters tested were intestinal crypt survival, lethality and intestinal crypt cellularity. The results showed both compounds to be good protectors in animals. The crypt survival curve for roentgen-irradiated mice treated with AET was parallel to that of the untreated group and was displaced to the right by 4.88 Gy (488 rad). Protection from neutron irradiation was less effective with a displacement of only 0.69 Gy (69 rad). Pretreatment with WR-77913 increased the slope of the crypt survival curve in roentgen-irradiated mice. This was also seen to a much less extent in neutron-irradiated animals. The displacements of the curves (at 50 per cent crypt survival) were found to be 5.15 and 1.02 Gy (515 and 102 rad) for roentgen and neutron irradiation, respectively. The lethality experiments showed a dose modification factor (DMF) of 1.42 for both drug-tested groups of roentgen-irradiated mice. The dose modification factors for fission neutron irradiated mice were 1.48 and 1.2 for WR-77913 and AET-treated mice, respectively. The effect of these protectors of crypt cellularity is also discussed.