Effect of Ovariectomy on Mammary Gland Expression of TGFα and EGFR mRNAs and its Relation to Mammary Gland Involution in Mice

Abstract

To understand the relationship between transforming growth factor α (TGFα) and mammary gland involution, changes in the growth of normal and preneoplastic mammary glands, the expression of TGFα and epidermal growth factor receptor (EGFR) mRNAs in the mammary gland, and serum prolactin (PRL) level were examined in 3-month-old virgin SHN mice 4 to 108 days after ovariectomy (OVX). The formation of normal end-buds and preneoplastic hyperplastic alveolar nodules was significantly reduced after 9 days of OVX, associated with the decreased serum PRL level. Both TGFα and EGFR mRNA expression in the mammary glands declined 18 days after OVX. Thereafter, TGFα mRNA tended to increase, while EGFR mRNA continued to decrease. These observations suggest that the decline of both estrogen and PRL play major roles in the mammary gland involution after OVX, and that the decline of EGFR, through which TGFα manifests its effects, play a secondary role in this process.