PARENT SESSION

(M622) EXPRESSION OF ANTI-MULLERIAN HORMONE DURING THE DEVELOPMENT OF BOVINE FETAL OVARIES.

Fortune, Joanne¹, Yang, Ming¹, ¹ Cornell University, Ithaca, NY

ABSTRACT- Mechanisms controlling early preantral follicular development are poorly understood. Evidence suggests that activation of primordial follicles and subsequent follicular growth are regulated by both stimulatory and inhibitory factors, but little is known about how follicular development is restricted. Durlinger et al. reported that anti-Mullerian hormone (AMH) inhibits activation of mouse primordial follicles (2002) and attenuates FSH-stimulated growth of preantral follicles (2001). In cattle, AMH inhibits the growth of primary follicles activated in vitro and there is indirect evidence suggesting that it also inhibits activation of primordial follicles. To further investigate the role of AMH in bovine folliculogenesis, AMH protein expression was assessed in bovine fetal ovaries at various gestational ages by immunohistochemistry. Fetal ovaries were obtained from a local slaughterhouse and grouped based on the following expected transitions in follicular development: 1) day 80 - 90, no follicles present (n = 4); 2) day 91 - 140, primordial follicles present (n = 6); 3) day 141 - 210, primary follicles appear (n = 5); 4) > 210 days, a few secondary follicles observed (n = 5; gestational age estimated by crown-rump length; length of bovine gestation = 281 days). In fetal ovaries < 211 days of gestation, AMH expression was completely absent in germ cells and in primordial and primary follicles. AMH-positive staining was first observed in fetal ovaries > 210 days of gestation and AMH immunoreactivity was limited to the cytoplasm of granulosa cells (GCs) of follicles at certain developmental stages. No GCs of primordial follicles expressed AMH and GCs of primary follicles were rarely AMH positive. Stronger AMH expression was observed in the GCs of most secondary follicles and in small (< 2 mm) antral follicles and their cumulus cells. AMH was not detected in theca or stromal cells. In summary, the onset of AMH expression occurs during the last 2 months of gestation in cattle and the degree of AMH immunoreactivity is correlated with the stage of follicular development. The results support the hypothesis that in cattle AMH from secondary follicles inhibits the growth of earlier follicular stages (Supported by USDA #2003-35203-13532)

KEY WORDS: Ovary, Follicular Development, AMH, Cattle