Effects of Porcine Follicular Fluid Added to the Maturation Medium on Fertilization and Development into the Two-Cell Stage of Rat Follicular Oocytes in Vitro.

A study was undertaken to examine the in vitro fertilization and development into the 2-cell stage of rat follicular oocytes matured in modified Krebs-Ringer solution (mKRB) supplemented with procine follicular fluid (pFF). The oocytes were recovered at 0, 4, or 8 hours (h) after hCG injection from follicles (F-0, F-4, or F-8 oocytes) of immature rats pretreated with PMSG. F-0 to F-8 oocytes were cultured in mKRB with or without 10% or 20% pFF for 12 to 4h. After maturation culture, these oocytes were transferred into sperm-suspended mKRB solution (4-14×105 sperm/ml) and culture continued for 36 h. When F-0 to F-8 oocytes were matured in mKRB alone, the fertilization rates were low (28.2% of F-0 oocytes to 62.7% of F-8 oocytes). These rates markedly increased to 80.5 to 87.6% in oocytes matured in mKRB with pFF (P<0.01). Furthermore, a high incidence of 2-cell embryos was obtained in oocytes cultured in mKRB with pFF (75.8-78.2%, P<0.01). The maturation processes did not differ between oocytes cultured in mKRB with and without pFF, and those matured in vivo. These results indicate that addition of pFF to the maturation medium improves fertilization rates and development into the 2-cell stage of rat follicular oocytes. This pFF action appears to be non-specific for rat oocytes.