Follicle-stimulating hormone increases ovarian vein nonsteroidal factors with gonadotropin-inhibiting activity

Normally cycling monkeys were treated with 50 IU/day of 'pure' follicle-stimulating hormone (FSH) on days 1 through 11 of the menstrual cycle. Ovarian venous serum (OVS) was collected on day 10; then all right ovarian follicles were aspirated. On day 11, OVS was collected again. Gonadotropin-inhibiting activity was determined in each sample by measuring the suppression of gonadotropin secretion by rat anterior pituitary cells in culture. OVS obtained on day 10 suppressed basal FSH secretion by ~45% and luteinizing hormone-releasing hormone stimulated luteinizing hormone secretion by ~50% (P < 0.05, versus castrate serum). On day 11, OVS from the left ovary continued to suppress gonadotropin secretion, whereas OVS from the right ovary demonstrated significantly less gonadotropin-inhibiting activity. These findings demonstrate that exogenous FSH increases OVS concentrations of a nonsteroidal ovarian factor(s) with gonadotropin-inhibiting activity.