Abstract
Summary
Spontaneous mammary cancers were observed in 4 female rats among a total of 28 (7♂ and 21♀) offspring of mothers treated with 3-methylcholanthrene before pregnancy. These tumors developed at the age of 49. 85. 90. and 90 days. Histologically, 3 were mammary adenocarcinoma and 1 an undifferentiated breast cancer. One female rat among a total of 12 (3♂ and 9♀) offspring of mothers treated with 3-methylcholanthrene during pregnancy developed spontaneous mammary cancer at the age of 200 days. No mammary cancer was observed in rats whose mothers were fed 3-methylcholanthrene during lactation. Also, injection of cell-free filtrate prepared from the mammary cancer induced with 3-methylcholanthrene to the normal newborn rats of less than 24 hours old failed to induce mammary tumors in these animals. These observations are of great interest for further investigation.
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