ADAPTIVE RESPONSE IN EMBRYOGENESIS - I - DOSE AND TIMING OF RADIATIONFOR REDUCTION OF PRENATAL DEATH AND CONGENITAL-MALFORMATION DURING THE LATE PERIOD OF ORGANOGENESIS

An adaptive response was demonstrated during embryogenesis in mice. Wh ole-body irradiation at a dose of 0-50 cGy was given to condition preg nant ICR mice on day 9 to day 11 of gestation, Then their whole bodies were exposed to a challenging dose of 5 Gy on the next day. The numbe rs of living fetuses, prenatal deaths and living fetuses with external gross malformations were determined on day 19. A conditioning dose of 30 cGy on day 11 significantly increased the rate of living fetuses a nd reduced the incidence of congenital malformations induced by a 5-Gy dose on day 12. This indicates the existence of a critical dose and t iming for administering a conditioning dose for radioadaptation during the late period of organogenesis in mice. The possible mechanisms inv olved are discussed. (C) 1998 by Radiation Research Society.