Decline of follicular oocyte maturation inhibitor coincident with maturation and achievement of fertilizability of oocytes recovered at midcycle of gonadotropin-treated women.

Abstract

To examine whether a decline in follicular oocyte maturation inhibitor (OMI) is associated with attainment of oocyte maturation and fertilizability, OMI was measured in follicular fluid (FF) of 39 follicles of 20 normal women given human menopausal gonadotrophin and human chorionic gonadotropin to induce follicular growth and maturation. Oocytes were aspirated per laparoscope, the fluid was saved, and the egg was observed, incubated, and inseminated with the husband's sperm. Concepti that developed to the 4-to 8-cell stage were transferred to the uterus and the women were followed for pregnancy. OMI activity in each FF was measured by using cultured cumulus-enclosed porcine oocytes (30-40 oocytes per FF sample). Estrogen, progesterone, and A4-androstenedione were measured in FF by radioimmunoassay. The FF of 13 preovulatory follicles yielding oocytes that were mature and fertilizable had significantly less OMI activity (mean ± SEM) (0.58 ± 0.10 unit/ml) compared to follicles yielding immature oocytes (2.8 ± 0.56 units/ml; n = 9), atretic oocytes (5.5 ± 2.5 units/ml; n = 7), or preovulatory oocytes with fractured zonae (1.9 ± 0.63 units/ml; n = 7). The estrogen concentration (mean ± SEM) of prevulatory follicles yielding mature fertilizable eggs or mature eggs with fractured zonae was greater (396 ± 34 ng/ml; n = 20) compared to follicles yielding immature or atretic eggs (203 ± 59 ng/ml; n = 9 and 97 ± 47 ng/ml; n = 7, respectively; P < 0.05). Progesterone concentration (mean + SEM; ng/ml) of FF was generally elevated in all preovulatory follicles (635 ± 53) compared to immature or atretic follicles (230 -64 and-76 ± 17, respectively; P < 0.05). It may be concluded that in normal follicle maturation there is a decline in OMI in the follicle containing an oocyte that becomes mature and fertilizable. There is also an increase in estrogen, progesterone, and follicle size. It is also possible to have an abnormal follicle maturation when there is an increase in size as well as FF, estrogen, and progesterone, but without a decline in OMI-a situation which can lead to production of a nonfertilizable oocyte.It is well documented that the human oocyte completes its meiotic maturation within the dominant preovulatory follicle within 30-48 hr prior to ovulation (1, 2). It is believed that the preovulatory gonadotropin surge brings this maturation about; yet the mechanism is poorly understood. Oocyte maturation only occurs within the dominant mature follicle and not in the adjacent less mature follicles. Several investigators in this laboratory have partially purified an oocyte maturation inhibitor (OMI) from immature porcine follicles, which may play a role in keeping the oocyte in the immature dictyate state (3-6).Whether a decline in OMI at the time of ovulation is the cause of oocyte maturation is not known. Furthermore, the mechanisms responsible for choosing the dominant follicle to be ovulated are not well understood. The purpose of this study was to measure changes in OMI in preovulatory human follicles and...

Relationships between follicular fluid steroid hormone concentrations, oocyte maturity, in vitro fertilization and embryonic development in the rhesus monkey

“…We did not find the correlation between higher E, concentrations and oocyte maturity reported in human studies (Channing et al, 1983;Botero-Ruiz et al, 1984). This lack of correlation has also been reported for spontaneous cycles (Cha et al, 1986).…”

Cumulus cells secrete a meiosi‐inducing substance by stimulation with forskolin and dibutyric cyclic adenosine monophosphate

“…The resumption of oocyte meiosis may not only depend on active stimulation. This process may also involve a removal of inhibitory signals, as previously proposed (Channing and Tsafriri, 1977;Channing et al, 1983). A change in the balance between inhibitory and stimulatory substances of the follicle fluid might be involved in the resumption of meiosis (Westergaard et al, 1984;review, Byskov, 1979).…”

Inhibition of progesterone‐mediated maturation of oocytes of Xenopus laevis by oocyte maturation inhibitor from pig follicular fluid: Development of a routine assay for the inhibitor with Xenopus oocytes

“…Cameron et a1 [1983] reported that human FFl inhibited the progesteronemediated meiotic maturation of Xenopus Zuevis oocytes. They concluded that the inhibition of Xenopus oocytes resulted from the OM1 against mammalian oocytes, which is present in this fluid [Channing et al, 1983;Chari et al, 19831. We have now standardized the Xenopus OM1 assay using a partially purified fraction from pig follicular fluid.…”