Basic Fibroblast Growth Factor in hyperplastic pituitaries of dopamine receptor D2 knockout female mice.

CAROLINA CRISTINA, MARÍA INÉS PEREZ-MILLÁN, GRACIELA DIAZ –TORGA, ADRIÁN GÓNGORA, ALBERTO BALDI, GARIELA SYCZ AND DAMASIA BECU-VILLALOBOS

Toronto CANADA

Simposio; The Enocrine Society. Toronto June 2007; 2007

The Enocrine Society.

Carolina Cristina, María Inés Perez-Millán, Graciela Diaz –Torga, Adrián Góngora, Alberto Baldi, Gariela Sycz and Damasia Becu-Villalobos,  Basic Fibroblast Growth Factor in hyperplastic pituitaries of dopamine receptor D2 knockout female mice.   Dopamine D2 Receptor knockout (KO) female mice develop chronic hyperprolactinemia and pituitary hyperplasia.  Recently, we have shown that they have an overexpression of vascular endothelial growth factor (VEGF) in folliculoestellate cells, suggesting a paracrine action of VEGF on pituitary endothelial cells (Endocrinology 146:2952:2005). Numerous growth factors modulate angiogenesis in different conditions. Among them, the type-2 Fibroblast Growth Factor (FGF2) exerts its mitogenic action on a wide variety of cells. We studied the expression of FGF2 and its receptor, FGFR1, in pituitaries from KO and wildtype (WT) female mice. We also evaluated FGF2 subcellular localization in relation to the development of pituitary hyperplasia, the effect of FGF2 on prolactin secretion, cell proliferation and phosphorylation of extracellular signal-regulated kinases (ERK) comparatively in pituitaries from WT and KO 8 month-old female mice. 1 and 10 ng/ml FGF2-induced prolactin release showed a similar pattern in both genotypes, even though basal release was higher in KOs. 10 ng/ml FGF2 stimulated pituitary cellular proliferation (MTS assay and 3[H]-Thymidine incorporation), and there were no differences between genotypes (P Interaction= 0.82, FGF: P= 0.0061 and 0.0042, respectively). The concentration of FGF2 (measured by ELISA) was lower in KO pituitaries (P<0.00001). Accordingly, FGF2 levels in pituitary cells cultured for five days was also lower in KO (P= 0.00014).  Immunofluorescence histochemistry showed less FGF2-immunoreactivity in pituitaries from KO females, and, it also revealed a distinct FGF2 localization pattern between genotypes, being predominantly nuclear in KO and cytosolic in WT sections. Nuclear indexes of FGF2 immunopositivity were 44.8 + 7.1 % in KO and 24.3 + 3.5 % in WT, P= 0.027. FGFR1 levels (Western blot and immunohistochemistry) were higher in KO pituitaries. Basal concentration of pERK was lower in KO cells (P= 0.018). But, when stimulated with FGF2 significant higher increment of ERK phosphorylation was evidenced by KO cells at 5, 10 and 15 min (P ≤ 0.02). We conclude that the disruption of the D2R caused and overall decrease in pituitary FGF2 levels, with an increased distribution in the nucleus, and increased FGFR1 levels. These results are important in the search for reliable prognostic indicators for patients with pituitary adenomas, in particular dopamine resistant prolactinomas, which will make tumor-specific therapy possible.