Peptide Growth Factors Modulate Prostaglandin E and F Production by Goldfish Ovarian Follicles
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This study examines the effect of epidermal growth factor (EGF) on prostaglandin synthesis by goldfish ovarian follicles at different developmental stages. Early vitellogenic follicles (EVIT), vitellogenic follicles (VIT), and prematurational full-grown follicles (PMFG) were examined. EGF alone had no effect on prostaglandin synthesis whereas production of PGE2 and PGF2alpha was enhanced in the presence of the eicosaniod precursor arachidonic acid (AA) in all three follicle classes. EGF enhanced AA stimulation of PGE2 production in both VIT and PMFG follicles. In the same follicles, AA-induced PGF2alpha production either was reduced or was unaffected by EGF. This suggests regulation of prostaglandin synthesis at a point downstream of the conversion of AA to PGH2: the precursor for both PGE2 and PGF2alpha. EGF had no effect on AA stimulation of either PGE2 or PGF2alpha in EVIT follicles. While only VIT and PMFG follicles were responsive to EGF, Western blotting with an antibody to the human EGF-receptor (EGF-R) suggests that all three classes of follicle may possess the receptor protein. Additional tests showed that insulin-like growth factor-I (IGF-I) had no effect on the production of either PGE2 or PGF2alpha by PMFG follicles. By comparison both TGFalpha (which binds to the EGF receptor) and TGFbeta (which acts through a different receptor) enhanced AA-stimulated PGE2 production while having no effect on AA-stimulated PGF2alpha production. In summary, this study demonstrates that several growth factors (EGF, TGFalpha, TGFbeta) may play a role in the regulation of ovarian prostaglandin synthesis and that the actions of EGF change during ovarian follicular development in the goldfish.
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