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 48months 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 48months; 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.