Studies on the adaptive response in mouse female germ cells X-irradiated in vitro at two different stages of maturation.
BACKGROUND
Radioadaptation is a phenomenon whereby cells exposed to a low dose of ionizing radiation are more resistant to a much higher dose delivered some time thereafter. This phenomenon could result from the activation of damage repair and/or antioxidant defense systems by the low dose.


METHODS
The existence of a cytogenetic adaptive response in female germ cells was investigated using a recently developed in vitro system. Mouse ovarian follicles were cultured from an early preantral stage up to ovulation. The follicles were X-irradiated with either 2 or 4 Gy ("challenge dose") preceded or not by 50 mGy ("conditioning dose", 5 h earlier), on days 0 or 12 of the culture. Ovulated oocytes were collected on day 13, fixed and analyzed for the presence of chromosome aberrations.


RESULTS
Irradiation with 2 or 4 Gy on days 0 or 12 did not influence ovulation but had dose-dependent effects on the germinal vesicle breakdown of the oocytes. It also caused dose-dependent chromosome damage, with a greater sensitivity of oocytes to this effect when irradiation occurred on day 12 than on day 0. Prior irradiation of oocytes with the dose of 50 mGy led to a reduction in the yield of chromosome aberrations when irradiation occurred on day 12 but not on day 0.


CONCLUSIONS
These results suggest that pre-irradiation of mouse pre-ovulatory oocytes with a low conditioning dose could confer on them some protection against radiation-induced chromosomal damage by a subsequent challenge dose of a few Gy.
Jacquet
Paul
P
Laboratory of Molecular and Cellular Biology, Institute for Environment, Health & Safety, Belgian Nuclear Research Centre, SCK*CEN, B-2400 Mol, Belgium. pjacquet@sckcen.be
Buset
Jasmine
J
Neefs
Miek
M
Vankerkom
Jean
J
D000222:Adaptation, Physiological / Q000235:genetics* / Q000528:radiation effects; D000818:Animals; D002478:Cells, Cultured; D002869:Chromosome Aberrations / Q000528:radiation effects; D003433:Crosses, Genetic; D020732:Cytogenetic Analysis; D004307:Dose-Response Relationship, Radiation; D005260:Female; D005854:Germ Cells / Q000502:physiology* / Q000528:radiation effects*; D066298:In Vitro Techniques; D051379:Mice; D008807:Mice, Inbred BALB C; D008808:Mice, Inbred CBA; D009865:Oocytes / Q000528:radiation effects*; D006080:Ovarian Follicle / Q000254:growth & development; D014965:X-Rays