TGF-1 in a prolactinoma experimental model: The Dopamine receptor D2 knock out mice (drd2 -/-).

MARÍA VICTORIA RECOUVREUX; MARÍA CLARA GUIDA; DAMASIA BECÚ-VILLALOBOS; GRACIELA DÍAZ -TORGA

San Diego

Congreso; ENDO 2010, San Diego, USA; 2010

The Endocrine Society

Prolactinomas are the most frequent pituitary tumors and they are usually benign. The dopamine type two receptor (drd2) is the predominant subtype in the anterior pituitary and mediates dopamine’s inhibitory actions on lactotrops. Because of the lack of dopaminergic inhibitory control, female drd2-/- mice develop prolactinomas: chronic hyperprolactinemia and lactotrope hyperplasia.  TGFβ1 is a potent multifunctional cytokine that regulates many biological functions ranging from growth/differentiation to apoptosis of various cell types. It is locally synthesized by lactotropes where it regulates cellular function, inhibits cell proliferation and prolactin synthesis. After synthesis TGFb remains tightly bound to its cleaved prodomain: latency associated peptide (LAP). In addition, before secreting, TGFb-LAP is disulfide bonded to a latent TGFβ-binding protein (LTBP). Once secreted the LLC remains covalently linked to the extracellular matrix. Dissociation from its latent complex is named TGF-β1´s “activation” , Due to their powerful effects on the cellular and molecular processes TGFb must undergo a highly regulated activation process to be functional. As it was recently suggested that TGFb1 might mediate, in part, dopamine inhibitory action on lactotropes in rats, the aim of this study was to evaluate total and active TGFb1 and its regulation by dopamine and estradiol in mice lacking drd2 (drd2-/-) and +/+  pituitary glands. ELISA was performed to quantify active or total TGFb1 content in pituitary homogenates with a TGFb1 Emax ImmunoAssay-System, PROMEGA. We found significantly lower active pituitary TGFb1 levels in both male and female  d2dr-/- mice when compared with their wild type counterparts (p<0.0001). There were also sexual differences, since female`s pituitaries showed lower active TGFb1 levels than males ones (p=0.0003). We didn’t find significant differences in pituitary “total TGFb1” levels. When we evaluated a possible  dopaminergic control on pituitary TGFb1 activity, we found that acute sulpiride ip (10mg/kg, 24hs) lowered active TGFb1 in females but not in males treated mice (p=0.01), but increased serum prolactin levels in both sexes. Cabergolin treatment (2mg/kg, 24hs) didn’t affect active TGFb1 in either sex, in spite of its clear effect on serum prolactin levels. Surprisingly estradiol treatment (0.2mg/kg sc, 24hs) increased active TGFb1 only in drd2-/- female mice pituitaries (p=0.013) but it didn’t affect active TGFb1 levels in drd2+/+ female or males (both genotypes), neither total TGFb1 in either sex or genotype as well. In summary we demonstrated differential active TGFb1 expression in d2dr-/- and +/+ mice, with lower levels in females, despite no differences in total TGFb1 between sexes and/or genotipes. Our results suggest a sexually differentiated dopaminergic and estrogenic control on pituitary active TGFb1, more sensitive in females, as is the lactotrops function. As we found changes on active but not on total TGFb1, we suggest, for the first time a dopaminergic and estrogenic control on cytokine “activation” process at pituitary level. On the other hand the lowerer active TGFb1 level in pituitaries d2dr-/- could be due to the absent drd2 dopaminergic action.