Secretion of Steroids, Growth Factors, and Cytokines by Immortalized Mouse

Abstract

The expression and function of gonadotropin receptors, and the secretion of steroids, transferrin, and cytokines were inves-tigated in three immortalized (single transfection with v-myc) mouse granulosa cell lines (GRMO1, GRMO1L, and GRMO2). A dose-dependent increase in progesterone production was obtained in GRMO1 and GRM02 cells after addition of LH, FSH, mod-ulators of the adenylate cyclase enzyme system, and cAMP analogues. The LH-induced release of progesterone was already de-tectable in GRM02 cells after 8 h and was related to incubation time and cell number. Both epidermal growth factor (EGF) and transforming growth factor a (TGFoa) induced the secretion of progesterone in GRM02 cells, while no effect was obtained with TGFP. LH receptor concentration was highest in the GRMO2 cell line. FSH receptor mRNA was visualized in GRMO1 and GRM02 cells. Aromatase activity in GRM02 cells was induced by androgens and inhibited by aromatase inhibitors. Whereas all cell lines were able to secrete transferrin, only in GRMOI cells was transferrin secretion increased significantly by LH. FSH did not affect transferrin secretion in the three cell lines, in contrast to forskolin or 8-bromo-cAMP. The immortalized mouse granulosa cell lines were able to express and release several growth factors. The expression and secretion of activin, inhibin, TGFI, EGF, TGFoa, insulin-like growth factor II, fibroblast growth factor (acidic and basic), platelet-derived growth factor, and interleukin-6 suggest an autocrine or paracrine role for these factors in follicular differentiation and function. In conclusion, these cells, derived from mural granulosa cells and immortalized in a preovulatory state, can be used t