Expression and regulation of mRNAs for insulin-like growth factor (IGF-I),IGF-binding protein-2, and LH receptor in the process of follicular atresia

Expression of mRNAs for IGF-I, IGF-binding protein-2 (IGFBP-2), and LH rece ptor (LHR) as well as their regulations during induced follicular atresia w as determined. ee-day-old female rats received 15 IU pregnant mare serum go nadotropins (PMSG). Through detection, it was demonstrated that apoptosis o ccurred in some small antral follicles after 48 h of PMSG treatment. At 96 h, apoptosis occurred in preovulatory follicles. At 120 h, numerous apoptot ic cells appeared in preovulatory follicles. IGF-I was mainly expressed in preantral and small antral follicles from 48 to 120 h. At 48 and 96 h, the theca cells of preantral and antral follicles expressed high level of IGFBP -2 mRNA. At 48 h, there were strong signals of LHR mRNA in granulosa cells, but the LHR signals in granulosa cells significantly decreased at 96 and 1 20 h (p<0.001). Both epidermal growth factor (EGF) and IGF-I inhibited apop tosis in preantral and antral follicles. Meanwhile, it was observed that EG F promoted IGF-I mRNA expression, and in preovulatory follicles, IGF-I stim ulated LHR mRNA expression. These results show that the interaction between ECF and IGF-I may be involved in the regulation of atresia of follicles at different stages of development.