Effects of GnRH agonists on the expression of developmental follicular anti-mullerian hormone in varying follicular stages in cyclic mice in vivo

Gonadotrophin-releasing hormone (GnRH) agonists (GnRHa) have been widely used to induce a state of downregulation for in vitro fertilization, and its direct effects on the pituitary are well known. However, the effects of GnRHa on the expression of anti-mullerian hormone (AMH) by follicles in varying stages in vivo remain to be fully elucidated. In the present study 84 cyclic mice were randomly divided equally into four GnRHa groups and three cyclic mice were used as a control group. The expression levels of AMH in follicles of varying stages between days 0 and 7 following GnRHa administration were quantified using immunohistochemistry. The expression of AMH in follicles at various stages revealed dynamic changes during the process of downregulation. AMH in primary follicles initially increased and then decreased gradually. In small and large preantral follicles and in granulosa cells (GCs) surrounding the oocyte of small antral follicles, the expression of AMH began to increase on day 1, was attenuated on day 2, and then increased to a peak. The expression levels of AMH in the GCs surrounding the basement membrane, in contrast to the GCs surrounding the oocyte, were significantly lower and did not increase on day 1. In all stages of follicles, the expression of AMH declined gradually between the peak level and last day of downregulation. On day 7, the varying follicular stages all expressed lower levels of AMH than on day 0. This decrease was more prominent in the higher dose groups, compared with the lower dose groups. In conclusion, GnRHa was observed to induce time-dependent changes in the expression of AMH at varying follicular stages, which occurred in a dose-dependent manner.