Peptide growth factors modulate prostaglandin E and F production by goldfish ovarian follicles

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 (VET), and prematurational, full-grown follicles (PMFG) were examined. EGF alone had no effect on prostaglandin synthesis whereas production of PGE(2) and PGF(2 alpha) was enhanced in the presence of the eicosaniod precursor arachidonic acid (AA) in all three follicle classes. EGF enhanced AA stimulation of PGE(2) production in both VIT and PMFG follicles. In the same follicles, AA-induced PGF(2 alpha) 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 PGH(2): the precursor for both PGE(2) and PGF(2 alpha). EGF had no effect on AA stimulation of either PGE(2) or PGF(2 alpha) 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 PGE(2) or PGF(2 alpha) by PMFG follicles. By comparison both TGF alpha (which binds to the EGF receptor) and TGF beta (which acts through a different receptor) enhanced AA-stimulated PGF(2 alpha) production while having no effect on AA-stimulated PGF(2 alpha) production. In summary, this study demonstrates that several growth factors (EGF, TGF alpha, TGF beta) 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. (C) 1998 Academic Press.