Inhibition of mouse embryo cleavage by a factor present in the human preovulatory follicular fluid

Human follicular fluids (hFF) inhibited the in vitro cleavage of mouse embryo and fertilized oocytes. This inhibitory effect occurred at all stages of embryonal development and was reversible at low concentrations of FF. Gel chromatography of FF revealed inhibitory activity in two fractions, corresponding to mol wt of 20,000 and 50,000 daltons. This factor(s) might contain peptide components, since it was activated by heat treatment and trypsin digestion. In spontaneous cycles, late follicular phase hFF had significantly higher inhibitory activity than early follicular phase hFF. There was no significant difference in inhibitory activity of hFF aspirated from patients treated with clomiphene citrate alone, a combination of clomiphene citrate and gonadotropins, or gonadotropins alone. There was a positive correlation between hFF inhibitory activity and hFF estradiol and a negative correlation with progesterone in individual FF samples. These findings suggest that the hFF inhibitory activity of mouse embryo cleavage correlates with the differentiation state of the granulosa cells.