Radioprotective effect of an acute non-specific inflammation in mice.

Protection against 8.7 Gy whole-body gamma-irradiation (lethal in 100 per cent of mice by 30 days) was observed in 90 per cent of mice bearing a one-day-old granuloma induced by polyacrylamide beads. When the inflammatory reaction was induced sooner or later a lower or null protection was obtained. A dose-effect relationship between the volume of injected beads and resulting radioprotection was established. The radioprotective effect depends only on the acute non-specific inflammation since hydrocortisone acetate injected into mice before the beads abolished this protection. This inflammatory pattern led to a dose reduction factor of 1.36 +/- 0.08 (P less than 0.05) for LD 50/30. A 90 per cent survival was observed in mice bearing a one-day-old granuloma when they were injected 1 h before 10 Gy with the granuloma acellular eluate (P less than 0.02 compared to a 50 per cent survival observed with polyacrylamide beads alone). Substances with a molecular weight higher than 300,000 are involved in the synergistic radioprotective effect of the granuloma-eluate association.