Acute effects of GnRF-induced gonadotrophin secretion upon ovarian steroid secretion in the ferret

The effects of an increase in endogenous gonadotrophin secretion on the production of oestradiol, progesterone, androstenedione and testosterone by the ovaries of anaesthetized anoestrous and oestrous ferrets were followed. Gonadotrophin secretion was enhanced by the injection of gonadotrophin releasing factor (GnRF), and serial blood samples were collected over 9 h for hormone assay. Thyrotrophic hormone releasing factor (TRF) or acetic acid were injected for control purposes. The plasma content of oestradiol in oestrous females was significantly higher than during anoestrus, but secretion of this steroid was not increased by any means. The plasma concentration of progesterone in anoestrous females was significantly higher than during oestrus. It was increased by GnRF in anoestrous ferrets and less markedly in oestrous females. The plasma concentration of androstenedione was raised by GnRF to a greater extent during anoestrus than during oestrus. Testosterone was present in higher concentration in the plasma during anoestrus than during oestrus, and the level was increased by GnRF administration. These findings indicate that the ovaries of the anoestrous ferret secrete significant quantities of steroid hormones, and that they respond readily to gonadotrophic hormone.