Radiation-induced mammary tumorigenesis in pseudopregnant rats mated with vasectomized partners.
Pseudopregnancy was induced in Wistar-MS female rats by mating with male rats 1 month after vasectomy. Pseudopregnant rats received whole-body irradiation with 2.6 Gy gamma-rays at day 7 of pseudopregnancy and were then implanted with a DES pellet as a tumor promoter. In the control groups, virgin 2.5 month-old rats, and normal pregnant rats at day 7 of pregnancy were also exposed to the same dose of radiation. The incidence of mammary tumors in rats irradiated in pseudopregnancy (52.6%) was significantly higher than that in the irradiated virgin rats (20.8%), but was not significantly different from that observed in rats irradiated in normal pregnancy (66.7%). The appearance of the first mammary tumor in the rats irradiated in pseudopregnancy occurred 4 months earlier than that in the normal pregnancy group. The proportion of adenocarcinomas in total tumors was 16.7, 0 and 38.5% in rats irradiated in pseudopregnancy, virgin and pregnancy groups, respectively. The incidence of adenocarcinomas was not significantly different among the three groups.
Inano
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The First Research Group, National Institute of Radiological Sciences, Inage-ku, Chiba-shi, Japan.
Suzuki
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D000230:Adenocarcinoma / Q000209:etiology; D000818:Animals; D005260:Female; D008297:Male; D008325:Mammary Neoplasms, Experimental / Q000209:etiology*; D009381:Neoplasms, Radiation-Induced / Q000209:etiology*; D011247:Pregnancy; D011555:Pseudopregnancy / Q000150:complications*; D051381:Rats; D017208:Rats, Wistar; D014659:Vasectomy; D014916:Whole-Body Irradiation