Differential radioprotection of three mouse strains by basic or acidic fibroblast growth factor

Recently we found that human recombinant basic fibroblast growth factor (FGF2) radioprotected C3H/HeNCr mice after whole body irradiation (WBI). The purpose of the present study was to compare the in vivo radioprotective effects of human recombinant acidic fibroblast growth factor (FGF1) or FGF2 in three strains of mice (C3H/HeNCr, BALB/CAn, C57BL/6). In vivo administration of 6 micrograms/mouse of FGF1 or FGF2 pre- or post- WBI significantly protected only C3H and BALB/C mice. Dose modification factor was: C3H(FGF1/2) 1.09 +/- 0.02/1.14 +/- 0.04; BALB/C(FGF1/2) 1.13 +/- 0.02/1.15 +/- 0.01. Response was minimal or absent in C57 mice (FGF2 1.02 +/- 0.02). Increasing the FGF dose above 12 micrograms/mouse did not increase radioprotection in any strain. In single radiation dose studies, FGF2 was more potent than FGF1 in C3H mice; FGF1 and FGF2 were equipotent in BALB/C mice; and both had minimal effect in C57 mice. Significant radioprotection occurred in only two of the three strains of mice studied. We therefore suggest caution in applying mouse radioprotection data to other species.