PARENT SESSION
SLIDE SESSION 2: FACTORS REGULATING EARLY FOLLICULAR DEVELOPMENT
Chairs: Evelyn Telfer, Robert Koos, Leanne Sleer (Trainee)
Univ Ottawa-UCU Auditorium
2:30 PM-4:30 PM
12
THE ARYL HYDROCARBON RECEPTOR (AhR) MAY REGULATE THE GROWTH OF OVARIAN FOLLICLES TO THE ANTRAL STAGE.
Benedict, Jamie1, Lin, Tien-Min2, Peterson, Richard2, Flaws, Jodi1, 1 2
ABSTRACT- The AhR is a ligand activated transcription factor that regulates the response to various environmental contaminants. Although little is known about the role of the AhR in normal ovarian function, we previously have shown that it may regulate the number of antral follicles in the mouse ovary. For example, mice lacking the AhR (AhRKO) mice have fewer antral follicles than wildtype (WT) mice on postnatal day (PND) 53. The mechanism by which the AhR influences the numbers of antral follicles is not understood. The AhR may regulate either the growth of follicles to the antral stage or the rate of atresia in antral follicles. Thus, the purpose of this study was to test the hypothesis that the AhR influences antral follicle numbers by increasing the number of follicles that grow to the antral stage or decreasing the number of follicles that undergo atresia. To test this hypothesis, ovaries were harvested from WT and AhRKO mice on PNDs 32-35 and 45. Serial sections were prepared for evaluation of follicle numbers and appearance. Healthy follicles were classified as those that contained an intact oocyte, organized granulosa cell layers, and few apoptotic bodies. Atretic follicles were classified as those that contained a degenerating oocyte, disorganized granulosa cell layers, and/or more than 10% of the granulosa cells were pyknotic. The results indicate that between PND 32-35 and PND 45, WT mice had a 1.7 fold increase in the number of antral follicles. On PND 32-35, WT mice had 4,173 ± 522 antral follicles and by PND 45, this number increased to 7,249 ± 635 antral follicles (n = 6, p ≤ 0.01). In contrast, AhRKO mice did not have a significant increase in the number of antral follilces between PNDs 32-35 and 45. On PND 32-35, AhRKO mice had 4,631 ± 604 antral follicles and by PND 45, AhRKO mice had 5,333 ± 729 antral follicles (n = 6, p ≤ 0.52). The data also indicate that there was no significant difference between the number of atretic follicles in AhRKO and WT mice (WT: 21.3 ± 1.5% atretic follices and AhRKO: 24.4 ± 6.7% atretic follicles; n = 3, p ≤ 0.52) on PND 45. These results suggest that the AhR may regulate the growth of follicles to the antral stage, but it may not alter the rate of atresia in the mouse ovary. Supported by NIH grant 1RO1 HD 38955-01A1 (JAF) and NIH grant ES01332 (REP).
KEY WORDS: antral follicle, ovary, transgenic