Involvement of mitogen-activated protein kinase in transforming growth factor α-stimulated cell proliferation in the cultured granulosa cells of the Japanese quail

Abstract

The avian granulosa cells proliferate during follicular growth phase and differentiate to produce progesterone in response to luteinizing hormone (LH) when the follicle becomes the largest. In order to study the involvement of mitogen-activated protein (MAP) kinase in proliferation of the granulosa cells in avian species, quail granulosa cells were cultured for 66 h with various hormones (follicle stimulating hormone (FSH), LH, progesterone, estradiol-17β, testosterone), or growth factors (transforming growth factor α (TGF α), epidermal growth factor (EGF), insulin-like growth factor I (IGF-I), IGF-II), and the presence of immunodetectable MAP kinase was examined in the cell lysates. When the granulosa cells were cultured with TGF α, the cell number as well as the incorporation of [ 3H]thymidine was increased. Other hormones or growth factors caused no significant increase in cell numbers. Stimulation of the cells with TGF α for 10 min caused a retarded mobility of MAP kinase in the gel of SDS-PAGE. Both the increases in [ 3H]thymidine incorporation and the retarded mobility were inhibited by the presence of a tyrosine kinase inhibitor, genistein, indicating the importance of phosphorylation of protein during the TGF α-stimulation.