Expression and Regulation of Transforming Growth Factor B1 in Cultured Normal and Neoplastic Rat Pituitary Cells

Pituitary prolactin (PRL) cell gene expression and proliferation are regulated by hormones and growth factors. Transforming growth factor beta (TGFB) and blast growth factor (bFGF) have been implicated in the regulation of antenor pituitary function. To study the roles of TGFB and bFGF in anterior pituitary cell function, we analyzed normal and neoplastic pituitary cells in serum-free media. The various isoforms of TGFB and TGFB receptor types I, II, and III were also analyzed by reverse transcription-polymerase chain reaction (RT-PCR) in pituitary cells. Transforming growth factor beta 1 (TGFB1) stimulated PRL expression and PRL cell proliferation in normal pituitary. TGFB1 stimulated PRL expression, but inhibited proliferation in the growth hormone (GH) and PRL-producing GH(3) cells. Estradiol 17 B (E(2)) and bFGE stimulated PRL gene expression in normal pituitary and GH(3) cells, whereas E(2) inhibited and bFGF stimulated TGFB1 mRNA levels in normal pituitary PRL cells, but not in GH(3) cells. Both normal pituitary and GH(3) cells expressed the mRNAs for TGFB1, TGFB2, and TGFB3 isoforms and for TGFB receptors I, II, and III. These results indicate that there is a relative loss of regulatory control by growth factors in neoplastic GH(3) cells compared to normal pituitary PRL cells.