Immunolocalization of alpha-transforming growth factor in the developing rat mammary gland in vivo, rat mammary cells in vitro and in human breast diseases.

Immunoreactive alpha-transforming growth factor (alpha-TGF) was shown by immunocytochemistry to be present in the rat mammary gland at various stages of development, the staining being most intense in mature myoepithelial cells. Alpha-TGF was also detected in the secretions of the mammary glands of pregnant and lactating rats. alpha-TGF in the extracts of rat mammary glands at each stage of development, and in several rat mammary cell lines and in culture medium in which they had been grown, was shown by Western blotting to consist primarily of a protein of molecular weight 50 kDa. The amount of this protein was greater in the mammary gland of the lactating rat than in resting or involuting glands. alpha-TGF was also found in some, but not all, human breast carcinomas, and in benign hyperplastic breast diseases.