We have previously shown that MXC increases the percentage of atretic antral follicles and reduces the number of antral follicles in the mouse ovary; however, to our knowledge, these are the first experiments to show that the mechanism through which MXC induces atresia involves the Bcl-2 pathway. Specifically, the results of our study suggest Bax protein plays an important role in MXC-in-duced atresia, for we saw increased expression of Bax in the ovaries of MXC-treated CD-1 mice compared with the sesame oil-treated mice.
In addition, mice deficient in Bax protein were protected from an increase in the percentage of atretic follicles when treated with MXC. Further, the results of these studies indicate that, although there was an increase in the percentage of atretic follicles in MXC-treat-ed wild-type littermates from the BaxKO strain vs. sesame oil-treated wild-type mice from the BaxKO strain, there was no significant change in the total number of antral follicles between MXC-treated wild-type mice and sesame oil-treated wild-type mice. These data suggest that sufficient time may not have elapsed to see an actual change in antral follicle numbers in response to MXC.