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 30 follicles of 20 normal women given human menopausal gonadotropin 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 husban''s sperm. Concepti that developed to the 4-8 cell stage wree 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 .DELTA.4-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 .+-. standard error of the mean]) (0.58 .+-. 0.10 U/ml) compared to follicles yielding immature oocytes (2.8 .+-. 0.56 U/ml; 9), atretic oocytes (5.5 .+-. 2.5 U/ml; 7), or preovulatory oocytes with fractured zonae (1.9 .+-. 0.63 U/ml; 7). The estrogen concentration (mean .+-. SEM) of preovulatory follicles yielding mature fertilizable eggs or mature eggs with fractured zonae was greater (396 .+-. 34 ng/ml; 20) compared to follicles yielding immature or atretic eggs (203 .+-. 59 ng/ml; 9 and 97 .+-. 47 ng/ml; 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 L 0.05). 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 and FF, estrogen, and progesterone, but without a decline in OMI a situation which can lead to production of a nonfertilizable oocyte.