Figure 7. The possible pathways by which cortisol injection of female mice diminishes oocyte developmental competence.

Cortisol injection increases the level of glucorticoids (GC) in blood and ovary. Within the ovary, the GC elevation activates the Fas/FasL system and decreases levels of growth factors and the E2/P4 ratio by down-regulating the expression of GR. The activation of Fas/FasL and the decrease in growth factors and E2/P4 ratio work together to induce apoptosis of ovarian cells, leading to a decline in growth factor levels and E2/P4 ratio but an increase in FasL in the follicular fluid (FF). The increase in FasL and the decrease in growth factor levels and the E2/P4 ratio in FF cause apoptosis in both CCs and oocytes, impairing oocyte developmental potential. Furthermore, the apoptotic CCs also produce FasL that affects oocytes by acting on their Fas receptors.