Oocyte maturation inhibitor activity in human follicular fluid: quantitative determination in unstimulated and clomiphene citrate- and human menopausal gonadotropin-stimulated ovarian cycles.

Since removal of the oocyte from the intrafollicular milieu allows meiotic resumption and germinal vesical breakdown to proceed, the concept of an intrafollicular oocyte maturation inhibitor (OMI) has evolved. Accordingly, we asked the following questions: Is there OMI activity in human follicular fluid? Does OMI activity change with ovarian hyperstimulation? and Does OMI activity correlate with oocyte fertilization or the concentration of steroids in the corresponding follicular fluid? Fresh cumulus enclosed porcine oocytes from small follicles were incubated with human follicular fluid aspirates from normally menstruating patients with or without treatment: unstimulated follicles (N = 10), clomiphene citrate (150 mg/day) (N = 10)-treated cycles, and human menopausal gonadotropin (hMG) (N = 12)-treated cycles. A lyophylized porcine follicular fluid standard and serum-free culture media were used as positive and negative controls, respectively. After a 40-hr incubation with test materials, the oocytes were fixed, stained, and evaluated for oocyte maturation as determined by germinal vesical breakdown. Human follicular fluid, estradiol, progesterone, androstenedione, and testosterone levels were determined by radioimmunoassay. The 50% inhibitory dose (ID50) for OMI activity in follicular fluid from untreated, spontaneously menstruating women was less than that for follicular fluid from clomiphene-stimulated patients, which was less than that for follicular fluid from hMG-stimulated patients. The difference between OMI values from untreated and hMG-stimulated follicular fluids was statistically significant. Human oocytes removed from follicular fluid with higher OMI activity tended not to fertilize in vitro compared to the relatively lower OMI activity present in follicular fluid yielding oocytes which did fertilize.(ABSTRACT TRUNCATED AT 250 WORDS)