Effect of fetal age and method of recovery on isolation of preantral follicles from bovine ovaries

The objective of this study was to compare enzymatic and mechanical methods , at distinct fetal ages, on isolation of different developmental stages of preantral follicles from bovine ovaries. Fetal ovaries were obtained from pregnant cattle at 150 to 270 d of gestation, and 135,521 preantral follicl es at different stages of development were studied. The dissociation of ova ries with a mechanical procedure resulted in an average of 938.16 preantral follicles. In contrast, 3,715.56 follicles were obtained when enzymatic di gestion was used (P=0.0001). Histological evaluation confirmed follicular s tages and demonstrated that both mechanical and mechanical-enzymatic proced ure did not affect the cellular integrity of the follicles. Granulosa cell- oocyte complexes surrounded by a basal membrane, were considered preantral follicles in this study. The ratio of different stages of isolated preantra l follicles was significantly (P=0.0001) correlated to fetal age. The earli est fetal age at which tertiary follicles were identified was at 210 d of g estation. The results confirm previous observation that follicular developm ent and atresia are initiated during fetal development These data provide i nformation on methodologies to isolate intact bovine preantral follicles fo r investigating the control and regulation of follicular development and th e growth of preantral follicles in vitro. (C) 1999 by Elsevier Science Inc.