Influence of human chorionic gonadotropin (hCG) and hCG internalization by granulosa cells on the rate of in vitro fertilization and embryonic development of human oocytes.

Follicular fluids and granulosa cells were obtained from 28 aspirated follicles of nine women undergoing laparoscopy in an in vitro fertilization program. Follicular growth was stimulated by a human menopausal gonadotropin regimen and laparoscopy was performed 32 hours after human chorionic gonadotropin (hCG) administration. Follicular fluid 17 beta-estradiol (E2) levels were higher and hCG levels were lower in follicles with oocytes that fertilized and cleaved beyond two blastomeres (greater than two-cell group) than in those with nonfertilizable oocytes (NF group) (P less than 0.05). Compared to those from the NF group, granulosa cells from the greater than two-cell group secreted less progesterone (P) in vitro and had a fourfold increase in percentage of cells with internalized hCG. These results demonstrate that the steroidogenic capacity of granulosa cells from follicles whose oocytes fertilize and undergo accelerated embryonic development in vitro differs from the capacity of granulosa cells from NF follicles. This difference may be due to their enhanced ability to bind and subsequently internalize hCG.