Estrogens modulate the inhibitory effect of tumor necrosis factor-α on anterior pituitary cell proliferation and prolactin release

Considering that tumor necrosis factor-α (TNF-α) is involved in normal tissue homeostasis and that its receptors are expressed in the anterior pituitary, we examined the expressed in the anterior pituitary, we examined the effect of this cytokine on pituitary cell growth. Because anterior pituitary function depends on hormonal environment, we also investigated the influence of gonadal steroids in the effects of TNF-α on cell proliferation and the release of PRL from anterior pituitary cells. In addition, the release of TNF-α and its action on the release of PRL from anterior pituitary cells of rats at different stages of the estrous cycle was evaluated. In minimum essential medium D-valine, a medium that restricts fibroblastic proliferation, TNF-α (10 and 50 ng/mL) reduced 3H-Thymidine incorporation, DNA content, and active cell number. TNF-α failed to affect proliferation of cells from ovariectomized (OVX) rats. However, it significantly inhibited growth of cells from OVX rats cultured with 17ß-estradiol (E2) (10−9M) and from chronically estrogenized rats. TNF-α decreased the release of PRL from cells of intact rats, especially in proestrous, OVX rats cultured with E2 and chronically estrogenized rats. The release of anterior pituitary TNF-α was higher in proestrous rats. These results indicate that TNF-α plays and inhibitory role in anterior pituitary cell growth and the release of PRL in an estrogen-dependent manner.