Brief Communication: Hyperplasia of Rat Mammary Gland In Vitro 2

Rat mammary gland explants placed in organ culture underwent intraductal hyperplasia in the presence of insulin. The hyperplasia reached its maximum at about 2 weeks of culture and exhibited several morphologic variations. By ultrastructural criteria, it was shown that the proliferating cell was derived from the epithelial rather than the myoepithelial component of the ductal lining cells. Testosterone, added at the beginning of the experiment, partially inhibited the hyperplastic process.