Effects of ovariectomy and prolactin on mammary gland expressions of transforming growth factor alpha and epidermal growth factor receptor mRNAs in mice

摘要

Beginning 15 days after ovariectomy (OVX), a high mammary tumour strain of SHN virgin mice at 3 months of age received subcutaneous injections of danazol (0.5μg/0.1 ml olive oil, once/day), perphenazine (0.05 mg/0.1 ml saline, twice/day) or ovine prolactin (oPRL: 0.25 mg/0.05 ml buffer, twice/day) for 3 days to modulate their circulating PRL levels. Serum PRL was significantly decreased by danazol and increased by perphenazine compared with the intact and OVX-control groups. The expression of transforming growth factor-alpha (TGFalpha) messenger RNA (mRNA) and epidermal growth factor receptor (EGFR) mRNA in the mammary gland was increased by danazol. However, TGFalpha mRNA expression was decreased by perphenazine. Mammary end-bud formation was inhibited in the danazol-treated group. All findings suggest that the manifestation of the effect of TGFalpha on mammary gland was suppressed by PRL, while mammary gland growth required PRL, i.e. PRL was dominant to TGFalpha for mammary gland growth. OVX resulted in a significant decrease of TGFalpha mRNA expression in the mammary gland despite little change in serum PRL, confirming the previous observations. A similar trend was observed in ICR mice, however, the response to hormonal modulation was generally less susceptible than in SHN mice.