Relationship between oocyte apoptosis and ovarian tumours induced by high and low LET radiations in mice.
OBJECTIVE
To investigate the biological effectiveness of neutrons at the energy below 1 MeV on apoptosis and carcinogenesis in the mouse ovary.


METHODS
Female mice were exposed to 1.0 Gy monoenergetic neutrons (0.317, 0.525 and 1.026 MeV), (252)Cf fission neutron (2.13 MeV) or (137)Cs gamma-rays at 7 days of age. Apoptosis of the oocyte and pregranulosa cells, and ovarian carcinogenesis were compared between the radiations. The efficiency of gamma-rays for granulosa cell tumorigenesis was tested by transplantation of the irradiated ovaries into non-irradiated mice.


RESULTS
The cumulative apoptotic index of oocytes was 77.9%, 65.6% and 41.6% for the 0.525 MeV neutron, 2.13 MeV neutron and gamma-rays, respectively. Follicles with apoptotic pregranulosa cells were 53.0%, 18.3% and 22.8% of cumulative index for the three groups. Tubular adenomas developed in the groups of monoenergetic neutrons (26.1%) and gamma-ray (35.5%), whereas granulosa cell tumours developed only in the gamma-ray groups (3.2% for 1.0 Gy and 15.6% for 3.0 Gy). Partial-body irradiation with 3 Gy gamma-rays to the ovaries induced granulosa cell tumours with an incidence of 27.3%.


CONCLUSIONS
Effectiveness of neutrons to cause apoptosis was higher for 0.525 MeV than for 2.13 MeV. The pregranulosa cell apoptosis occurred in an oocyte-prone manner. The higher effectiveness of neutrons than gamma-rays to induce oocyte and pregranulosa cell apoptosis correlates with the inhibition of granulosa cell tumour development.
Nitta
Y
Y
International Radiation Information Center, Research Institute for Radiation Biology and Medicine, Hiroshima University, 1-2-3 Kasumi, Minami-ku Hiroshima 734-8553, Japan. yumiko@hiroshima-u.ac.jp
Hoshi
M
M
D000367:Age Factors; D000818:Animals; D017209:Apoptosis / Q000528:radiation effects*; D005260:Female; D005720:Gamma Rays / Q000009:adverse effects; D006107:Granulosa Cells / Q000166:cytology / Q000378:metabolism / Q000528:radiation effects; D007150:Immunohistochemistry; D018499:Linear Energy Transfer; D051379:Mice; D008809:Mice, Inbred C3H; D008810:Mice, Inbred C57BL; D009381:Neoplasms, Radiation-Induced / Q000209:etiology* / Q000473:pathology; D009865:Oocytes / Q000166:cytology* / Q000378:metabolism / Q000528:radiation effects*; D010051:Ovarian Neoplasms / Q000209:etiology* / Q000473:pathology; D010053:Ovary / Q000378:metabolism / Q000473:pathology / Q000528:radiation effects / Q000637:transplantation; D018809:Proliferating Cell Nuclear Antigen / Q000378:metabolism
D018809:Proliferating Cell Nuclear Antigen