Authors: Matilde Lombardero Sergio Vidal Robert Hurta Alba Román Kalman Kovacs Ricardo V Lloyd Bernd W Scheithauer
Publish Date: 2006/08/30
Volume: 9, Issue: 2, Pages: 137-143
Abstract
Both vascular endothelial growth factor VEGF and its receptor Flk1 are expressed in normal pituitary cells and in the prolactin and growth hormoneproducing GH3 cell line of the rat thus suggesting autocrine/paracrine function Regulation of the Flk1 receptor system in pituitary cells is poorly understood but evidence suggests that upregulated growth factors play a role in its expression and activation To study the role of growth factors in this process we examined changes in VEGF and Flk1 expression in GH3 cells following varied exposure to βFGF EGF and TGFβ1 Immunofluorescence labelling and laser scanning cytometry were used to measure changes in VEGF and Flk1 expression Results showed that βFGF EGF and TGFβ upregulated the VEGF/FLK1 receptor system Distinct patterns of activation were detected At 2 hours EGF and TGFβ caused no significant changes in VEGF and Flk1 expression however βFGF upregulated VEGF expression in 99 of cells but only induced modest changes in Flk1 overexpression A similar percentage of cells overexpressed VEGF after 24hour incubation with βFGF but more prominent Flk1 overexpression was detected At 24 hours EGF and TGFβ1 induced a significant increase in both VEGF and Flk1 expression In summary our findings show that VEGF/Flk1 expression in pituitary cells may be altered by different growth factors This may affect angiogenesis and the progression of pituitary tumors
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