PARENT SESSION
SLIDE SESSION 6: REPRODUCTIVE TOXICOLOGY IN THE MALE AND FEMALE
Chairs: Janice Bailey, Rao Veeramachaneni, Christina Borgeest (Trainee)
Univ Ottawa-Monpetit 203
2:30 PM-4:30 PM

CHRONIC EXPOSURE TO DIBROMOACETIC ACID (DBA), A COMMONLY OCCURRING DISINFECTION BY-PRODUCT IN DRINKING WATER, DIMINISHES PRIMORDIAL FOLLICLE POPULATIONS IN THE RABBIT.

Bodensteiner, Karin¹, Veeramachaneni, Rao², Klinefelter, Gary³, Kane, Colleen², Higuchi, Ty², Moeller, Carol², Sawyer, Heywood², ^{1 2 3}

ABSTRACT- Exposure to DBA adversely affects spermatogenesis and fertility in rats and rabbits. To determine if DBA also affects folliculogenesis, four groups (n = 10) of female Dutch-belted rabbits were exposed daily to 0 (control), 1, 5, or 50 mg DBA/kg body wt beginning in utero from gestation day 15 throughout life. DBA was delivered in drinking water and average (± SE) delivered doses, computed on a weekly basis, were 0, 0.95 ± 0.03, 5.15 ± 0.2 and 47.85 ± 2.1 mg. Functionality of the endocrine axis/ovulatory response was assessed following an intramuscular injection of 10 g GnRH at 24 weeks of age. Number of ovulation sites, ovarian weights and gross abnormalities of the reproductive tract were determined at necropsy 24 hr after GnRH challenge. Ovarian weights and number of ovulation sites did not differ among treatment groups. Left ovaries were fixed in Bouin′s solution and processed for histopathology. Tissue blocks were serially sectioned at a thickness of 6 m. All healthy follicles present in a section were categorized into one of five follicle types: primordial, primary, small preantral, large preantral, or small antral, and the area of section measured. Atretic follicles were also recorded. Five sections were counted per animal. Total number of primordial follicles was 10,064; 9,890; 6,170; and 7,670 for animals in the 0, 1, 5, and 50 mg groups, respectively. Number of primordial follicles/mm2/ovary was lower in both 5 (p < 0.01) and 50 (p = 0.1) mg groups as average (± SE) counts were 7.8 ± 0.8, 7.8 ± 1.1, 4.5 ± 0.6, and 5.9 ± 0.6, in the 0, 1, 5, and 50 mg groups, respectively. Nine animals in the 5 mg group and 7 in the 50 mg group had fewer primordial follicles than the control median value (907). Follicular populations at all other stages of development, including small antral follicles, were similar and there was no difference in number of follicular remnants, necrotic oocytes or atretic follicles. Although chronic exposure to DBA did not appear to have an effect on follicular development or ovulation, DBA exposure did reduce the population of primordial follicles. The long-term health consequences of a decrease in primordial follicles are unknown, but it is very likely that reproductive senescence occurs earlier. This abstract does not necessarily reflect USEPA policy. Research supported by USEPA Cooperative Agreement CR826465-01-0.

KEY WORDS: dibromoacetic acid, ovary, follicle, rabbit