New Method for Detection of Mouse Mammary Tumor Virus. I. Influence of Foster Nursing on Incidence of Hyperplastic Mammary Nodules in BALB/cCrgl Mice

Summary

A method for the rapid detection of the mouse mammary tumor virus (MTV), with hormone-induced “noduligenesis” in the mammary glands of BALB/cCrgl mice as an indicator of MTV, is described. Male and female BALB/cCrgl mice were foster-nursed on various MTV-carrying and MTV-free mouse strains. The male test mice were gonadectomized when 35 days old. Beginning at 36 days of age, all mice received daily injections of estradiol plus deoxycorticosterone acetate for 90 days. Most of the animals were killed on the 22d day after the last hormone injection. Hyperplastic alveolar nodules were found in the mammary glands of 53 of the 82 mice fostered on MTV-carrying strains. Such nodules were absent from normal BALB/cCrgl mice and from all but one mouse fostered on MTV-free strains. It is concluded that a high incidence of noduligenesis following hormone treatment occurs only in those BALB/cCrgl mice in which the MTV has been introduced, and that the hormonal induction of hyperplastic alveolar nodules in this strain is a reliable and rapid method for the qualitative detection of the mouse mammary tumor virus.