In vitro inhibition of rat oocyte meiosis by human follicular fluid fractions.

We studied the effect of low molecular weight fractions of human follicular fluid (FF1) on rat oocyte meiosis and progesterone secretion by the granulosa cells. Steroid-free FF1 extracts were filtered through Sephadex G50 gel. One highly retarded fraction was obtained (GF-3), which was either used for testing or further purified by filtration on Sephadex G10, the G10-3 fraction of which was used for experiments. The GF-3 and G10-3 fractions of FF1 inhibited (in a dose-dependent and reversible manner) meiosis of isolated rat oocytes during a 4-h culture. Similarly treated fractions of serum had no effect. The inhibition was not abolished by ether extraction, trypsin treatment, heating to 56 degrees C for 1 h or boiling for 5 min, whereas heating to 105 degrees C for 18 h decreased the effect. Gonadotropin-stimulated progesterone secretion by cumulus and mural granulosa cells was also dose-dependently and reversibly inhibited by the GF-3 fractions. Our results confirm those obtained in earlier studies on porcine oocyte maturation inhibitor (OMI).