Effects of Ovariectomy and Prolactin on Mammary Gland Expressions of Transforming Growth Factor α and Epidermal Growth Factor Receptor mRNAs in Mice

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