Reduction of short-term radiation lethality by biological response modifiers given alone or in association with other chemical protectors.

The advantages gained by a combined treatment of different chemical protectors on short-term lethality of X-irradiated adult male mice have been studied. The following compounds were given alone or in a mixture of two or three compounds: 16,16-dimethyl PGE2 (PGE2), cysteine (Cys), glucan, glutathione (GSH), 5-hydroxytryptamine (5-HT), mercaptoproprionylglycine (MPG), or WR-2721. The survival of mice treated before X irradiation with the optimal dose of each radioprotector given separately shows that WR-2721 and 5-HT yield the best protection with dose reduction factors (DRFs) of 2.2 and 1.7, respectively. Cysteine, glucan, PGE2, MPG, and GSH, with DRFs of 1.4, 1.4, 1.2, 1.1, and 1.1, respectively, are less efficient radioprotectors. When PGE2 was combined with a low dose of WR-2721 (200 mg/kg), the protection increased in a synergistic way. The increase in protection offered by a combination of PGE2 with Cys, glucan, GSH, or 5-HT is less marked and the effect obtained is only additive. A synergistic action is also obtained with a combination of WR-2721 (200 mg/kg) and 5-HT (8 mg/kg) (DRF 2.7).