Protective effect of S-2-(3-aminopropylamino)ethylphosphorothioic acid against induction of altered hepatocyte foci in rats treated once with gamma-radiation within one day after birth.

We have investigated the protective effects of S-2-(3-aminopropylamino)-ethylphosphorothioic acid (WR2721) on the induction by radiation of altered hepatocyte foci in 150-day-old Sprague-Dawley rats. WR2721 (100 micrograms/g of body weight) was administered to selected groups of neonatal animals 30 min prior to the administration of single doses of ionizing radiation (150 or 300 rads). Two focus phenotypes, described by the histochemical markers gamma-glutamyltranspeptidase and iron exclusion, were quantitated through the use of serial frozen sectioning techniques and computer-assisted image analysis. Although radiation was capable of inducing foci, induction was much more effective in female than in male rats. WR2721, however, reduced the frequencies of radiation-induced foci at both radiation doses, with the protective effect more readily apparent in female animals. The modulation of foci formation by WR2721 in the neonatal rat system suggests that this compound and related aminothiols may be useful probes for examining mechanisms of mutagenesis and carcinogenesis induced by radiation or chemicals.