7:30 AM-10:00 AM
(88) FOLLICLE-STIMULATING HORMONE RESPONSIVENESS AND LEVELS IN MICE DEFICIENT IN THE ARYL HYDROCARBON RECEPTOR.
Benedict, Jamie1, Marion, S2, Hoyer, Patricia2, Flaws, Jodi1, 1 Program in Toxicology, Baltimore, MD2 Deparment of Physiology, Tucson, AZ
ABSTRACT- The AhR is a ligand activated nuclear transcription factor that mediates the toxicity of various environmental chemicals. Although the role of this receptor is unknown, studies suggest that it may have a role in ovarian development and function. Specifically, previous work in our lab has shown that AhR-deficient mice (AhRKO mice) have a reduced number of antral follicles compared to wild-type (WT) littermates and that this reduced number of antral follicles is likely due to a decreased rate of follicular growth between post-natal days (PNDs) 32-53. Since follicle-stimulating hormone (FSH) is known to regulate follicular growth, the purpose of this study was to test the hypothesis that the slow rate of follicular growth in AhRKO mice is due, in part, to altered levels of FSH. To test this hypothesis, we conducted both in vitro and in vivo experiments. For the in vitro experiments, antral follicles were isolated from ovaries of WT and AhRKO mice (PND 21-28). The follicles then were placed in cell culture wells containing supplemented a minimum essential medium. The diameter of each follicle was recorded daily in two perpendicular axes for 72 hours using an inverted microscope. For the in vivo studies, blood was collected from WT and AhRKO mice (PNDs 21-28) during diestrus and subjected to radioimmunoassay for the measurement of FSH levels. Our results indicate that there were no statistically significant differences in the rate of growth of antral follicles from WT and AhRKO mice in response to FSH (AhRKO = 149.4 ± 6.9 m versus WT = 151.1 ± 4.9 m at time 0 hours and AhRKO = 210.0 ± 16.0 m versus WT = 200.3 ± 10.5 m at time 72 hours; n = 11, p ≥ 0.50). In addition, there was no statistically significant difference in circulating FSH levels in AhRKO and WT mice (AhRKO = 3.34 ± 0.38 ng/ml; WT = 3.03 ± 0.32 ng/ml; n = 4; p ≤ 0.33). These data suggest that the slow rate of growth of antral follicles in AhRKO mice is not due to altered FSH levels or responsiveness. Thus, the slow growth of antral follicles in AhRKO mice may be due to a lack of response or function of other hormones, receptors, or growth factors. Supported by HD 38955.
KEY WORDS: Aryl Hydrocarbon Receptor (AhR), ovary, follicle stimulating hormone (FSH), antral follicle