Studies On Follicular Development And Atresia And Their Regulatory Mechanism In Goat

Generally, most of the follicles undergo atresia during their development in mammals, and only a few grow to maturation and ovulation. For many years, the mechanisms of follicular atresia have been one of the foci of study. Recently, with the development in studies on cell apoptosis, it has been proved that follicular atresia is a process of cell apoptosis. However, the endocrinological and molecular evens underlying follicular development and atresia and granulosa cell apoptosis in the goat has not been studied. In the present study, we conducted several experiments using goats as experimental material. The contents of this study can be summarized as follows: 1.Selection of methods for detecting apoptotic granulosa cells. 2. The changes of follicle development and steroid production during estrous cycle and their relationship. 3. The difference of percentage of apoptotic granulosa cells and levels of steroids and IGFs in follicle fluids in follicles with different degree of atresia 4.The effect of FSH on the number of follicles, granulosa cell apoptosis and levels of steroids and IGFs in follicle fluids and serum. 5. The effect of FSH and IGF-1 on the production of steroids by intact follicles cultured in vitro. 6. The effects of FSH and IGF-1 on apoptosis and production of steroids in granulose cells cultured in vitro. 7. The effect of FSH and IGF-1 on maturation of COCs and the apoptosis of cumulus. The results obtained are as follows:1. There was a significantly positive correlation between the percentage of apoptotic granulosa cells detected by the H.E staining and that through TUNEL.2. Granulosa cell apoptosis was a physiological phenomenon in follicles, and with the progress of atresia, the percentage of apoptotic granulose cells increased significantly. The percentage of apoptotic granulose cells in the healthy, slightly atretic and atretic follicles were 0.13+0.02, 0.32+0.02 and 0.51+0.02, respectively.3. There were different levels of steroids and IGFs in the fluid of follicles with different degrees of atresia, and this difference was correlated with the percentage of apoptotic granulosa cells.4. The number of different sized follicles, percentage of apoptotic granulose cells and levels of steroids changed during the estrous cycles.5. FSH increased the number of large and medium follicles significantly, but there was no significant change in number of small follicles. FSH stimulated the production of steroids and IGFs, and their levels changed differently in serum and follicular fluid.6. IGF-1 stimulated production of steroids by intact follicles cultured in vitro, but FSHshowed no such an effect.7. There was a spontaneous apoptosis in granulose cells cultured in vitro. FSH and IGF-1 inhibited granulose cell apoptosis and increased secretion of progesterone. FSH increased the production of IGF-1, but H89 blocked this effect8. FSH and IGF- I promoted the maturation of COCs and inhibited the apoptosis of cumulus cells. There was a negative correlation between the percentage of oocyte maturation and that of apoptotic granulosa cells.