Kiyoo Tanabe

The Role of Nonsteroidal Regulators in Control of Oocyte and Follicular Maturation

Publisher Summary This chapter discusses the role of nonsteroidal regulators in control of oocyte and follicular maturation. The ovarian follicle is bathed in a fluid rich in steroid hormones as well as nonsteroidal regulators which interact to serve to control its maturation, responsiveness to gonadotropins, as well as to lead to control of the maturation of its oocyte. The orderly maturation of an ovarian follicle and its oocyte is controlled by pituitary LH and FSH in concert with local intrafollicular regulators. The principal nonsteroidal follicular regulators are an oocyte maturation inhibitor, a luteinization inhibitor, a luteinization stimulator, FSH receptor binding inhibitor, and inhibin-F. OMI is a polypeptide

Follicular fluid inhibin activity and steroid levels in ovarian tissue obtained at autopsy from human infants from 18 to 200 days of age.

The ovaries of 25 human infants from 18 to 200 days of age were obtained at autopsy, and their follicular fluid was subjected to measurement of inhibin activity, estrogen, progesterone, androstenedione, and testosterone. Significant inhibin activity was present in all samples of follicular fluid (charcoal-treated) (138 +/- 19 U/10 microliter follicular fluid; 10,545 +/- 2758 U/ovary). There was a tendency for greater inhibin activity, follicular volume, and estrogen in infants from 18 to 59 days than in older infants. There was a significant positive correlation between follicular fluid volume, estrogen, and androstenedione, compared with follicular fluid inhibin content per ovary. It is possible that elevated serum follicle-stimulating hormone and luteinizing hormone observed early in life stimulates follicle growth, inhibin, and estrogen production. As a result of elevated inhibin and estrogen, the gonadotropins may be inhibited, which may cause a decline in follicular activity after 4 to 6 months.

Demonstration of a gradient in inhibin activity, estrogen, progesterone, and ∆4-androstenedione in follicular fluid, ovarian vein blood, and peripheral blood of normal women *

Ovarian vein serum from 3 subjects during the late follicular phase of the menstrual cycle had detectable inhibin activity, whereas ovarian vein serum of 12 other subjects during the early follicular phase and luteal phase had no detectable inhibin activity in a rat anterior pituitary cell culture assay. Subjects having detectable inhibin activity (102 +/- 47 U/100 microliters) had 1257 +/- 582 U/100 microliters inhibin activity in FF, whereas subjects having no detectable inhibin activity had FF levels of 711 +/- 203 U/100 microliters of inhibin activity. Estrogen levels of FF and ovarian vein serum of the group having detectable inhibin activity in ovarian vein serum were 282 +/- 239 ng/ml and 4.8 +/- 1.77 ng/ml, respectively. The estrogen content of FF and ovarian vein blood of the group having nondetectable inhibin activity in ovarian vein blood was 127 +/0 45 ng/ml and 3.03 +/- 0.6 ng/ml, respectively.

Inhibin activity and steroid hormone levels in ovarian extracts and ovarian vein plasma of female monkeys during postnatal development

Inhibin activity, follicle-stimulating hormone (FSH)-suppressing substance, estrogen, progesterone, and androstenedione were measured in charcoal-treated ovarian tissue and ovarian venous and peripheral blood of eight rhesus monkeys ranging from 12 to 48 months of age. All of the monkeys demonstrated inhibin activity in ovarian tissue, which, if expressed per milligram protein, was relatively constant throughout development. However, if the activity was expressed per ovary, the amount of ovarian FSH-suppressing substance increased between 26 and 48 months; it was present in detectable amounts in ovarian venous blood only in one 26-month-old monkey. Detectable levels of estrogen were present in ovarian venous blood of the 26-month-old and the 48-month-old monkeys but not in the younger monkeys. It is possible that the secretion of inhibin activity may be in part responsible for low levels of serum FSH observed prior to puberty, because it has been observed by others that bilateral ovariectomy in the prepubertal monkey can result in a rise in FSH and that administration of charcoal-treated ovarian follicular fluid can suppress serum FSH in castrated prepubertal and adult rhesus monkeys.