Platelet-derived growth factor selectively decreases prolactin production in pituitary cells in culture

Platelet-derived growth factor (PDGF) markedly reduced the production of PRL without affecting GH production in GH4C1 cells. The ED50 was 6 ng/ml (2 X 10(-10) M), and maximum inhibition occurred at 50 ng/ml (1.5 X 10(-9) M) PDGF. There was no acute effect of PDGF on PRL release. PDGF treatment decreased PRL production after a 24-h lag; suppression of the rate of PRL production became maximal between 24-48 h and persisted for at least 14 days in the continued presence of PDGF. There was no effect of PDGF on cell proliferation under the conditions used, and no effect on leucine uptake or incorporation into protein. PDGF altered the morphology of cells in a manner similar to that of epidermal growth factor and TRH, and caused the cells to become more adherent to the culture substrate. The actions of PDGF were similar in GH4C1 and GH3 cells, but in the non-PRL-producing GC cells, PDGF enhanced GH production. PDGF antagonized the PRL synthesis-stimulating activity of TRH. We conclude that PDGF can act directly on pituitary cells to decrease selectively the production of PRL.