Leukaemia inhibitory factor and interleukin 6 inhibit secretion of prolactin and growth hormone by rat pituitary MtT/SM cells

The rat pituitary cell line, MtT/SM, has the characteristics of somatomammotrophs. The cells secrete both prolactin (PRL) and growth hormone (GH). We examined the effects of cytokines such as leukaemia inhibitory factor (LIF), interleukin 6 (IL-6), oncostatin M and interleukin 11 on the secretion of these hormones by the cells. These cytokines stimulate proliferation of the cells and inhibit the secretion of PRL by 70-80% and that of CH by 50%. The, induce tyrosine phosphorylation of STAT3 in the cells. The cells containing PRL or GH decreased at 48 h after treatment of the cells with LIF or IL-6, These results suggest that the LIF/IL-6 family of cytokines inhibits the functions of mammotrophs and somatotrophs in the pituitary gland. (C) 2001 Academic Press.