Estrogen attenuates expression of calcitonin-like immunoreactivity in the anterior pituitary gland

Quercetin improves postpartum hypogalactia in milk-deficient mice via stimulating prolactin production in pituitary gland

Postpartum dysgalactia is a common clinical problem for lactating women. Seeking out the safe and efficient phytoestrogens will be a promising strategy for postpartum dysgalactia therapy. In this study, the postpartum mice within four groups, including control group, the model group, and the treatment groups intragastrically administrated with normal saline, bromocriptine, bromocriptine plus 17α-ethinyl estradiol, and bromocriptine plus quercetin, respectively, were used. The results showed that quercetin, a kind of natural phytoestrogen, could efficiently promote lactation yield and mammary gland development in the agalactosis mice produced by bromocriptine administration. Mechanically, quercetin, such as 17α-ethinyl estradiol, significantly stimulated prolactin (PRL) production and deposition in the mammary gland in the agalactosis mice determined by western blotting, quantitative polymerase chain reaction, and enzyme-linked immunosorbent assay, respectively. Furthermore, quercetin could increase the expression of β-casein, stearoyl-CoA desaturase, fatty acid synthase, and α-lactalbumin in the breast tissues that are responsible for the production of fatty acid, lactose, and galactose in the milk at the transcriptional level determined by quantitative polymerase chain reaction. Specifically, quercetin promoted primary mammary epithelial cell proliferation and stimulated prolactin receptor (PRLR) expression probably via AKT activation in vitro. In conclusion, this study indicates that estrogen-like quercetin promotes mammary gland development and lactation yield in milk-deficient mice, probably via stimulating PRL expression and release from the pituitary gland, as well as induces PRLR expression in primary mammary epithelial cells.

Calcitonin-like peptide containing gonadotrophs are juxtaposed to cup-shaped lactotrophs

Calcitonin (CT) is known to inhibit basal and TRH-stimulated prolactin release in cultured anterior pituitary cells in vitro and pituitary CT-like peptide (pit-CT) is synthesized and released by isolated anterior pituitary cells. However, the specific cell type containing pit-CT has not been identified. To determine this, double label immunohistochemistry was performed on pituitary sections from male rats using antisera for specific marker peptides of gonadotrophs, thyrotrophs, lactotrophs, somatotrophs, corticotrophs, and folliculo-stellate cells. CT was only colocalized with gonadotroph-specific markers and the distribution of pit-CT immunoreactive (IR) cells followed the patterns of gonadotroph distribution in male and female rats. Double and triple label immunohistochemistry using antiserum for CT, FSH, and PRL showed an apposition of calcitonin-like peptide containing gonadotrophs to cup-shaped lactotrophs. To examine whether pit-CT IR was altered, similarly to gonadotrophs, with known changes in PRL serum levels, studies were extended to ovariectomized, pregnant, and lactating rats. The area covered by pit-CT immunoreactivity and the tissue content of pit-CT significantly differed between physiological states and the pit-CT level was inversely related to the known PRL status. Pit-CT containing gonadotrophs were in all cases apposed to cup-shaped lactotrophs. These results provide histological support for previous studies proposing that pit-CT serves as a paracrine inhibitor of PRL release.