Abstract.
The purpose of this study was to investigate the kinetics and estrogen dependence of the facilitory progesterone action on LH and FSH secretion from pituitary cells under dynamic culture conditions. Anterior pituitary cells obtained from ovariectomized or intact adult Wistar rats were cultivated on Cytodex 1 microcarrier beads. The perifusion experiments were performed with four separate perifusion chambers. The cells of chambers I+II had been pretreated with medium containing vehicle (0.1% ethanol), those of chambers III + IV with medium containing 1 nmol/l estradiol for 48 h. After perifusion was started, each of the chambers was challenged with an initial 2-min GnRH (1 nmol/l) pulse. Chamber I was further perifused with medium containing vehicle, chamber II with medium containing vehicle + 100 nmol/l progesterone, chamber III with medium containing 1 nmol/l estradiol, and chamber IV with medium containing 1 nmol/l estradiol + 100 nmol/l progesterone. Three further GnRH pulses were administered at 50-min intervals to each of the chambers. In estradiolprimed cells from intact rats, progesterone induced a positive effect on LH and FSH secretion after 50 min of exposure to progesterone. After 100 min of progesterone treatment, LH and FSH release were enhanced to 420 and 500 per cent, respectively. When such cells were not primed with estradiol, a slight though insignificant positive action of progesterone on LH release was present after 50 and 100 min of treatment, whereas FSH secretion was not influenced. The facilitory effect of progesterone occurred only after 100 min when estradiol-primed cells from ovariectomized rats were used. LH and FSH secretion were only enhanced by up to 210 and 233 per cent, respectively. When these cells were not primed with estradiol the positive progesterone effect was absent. In conclusion, progesterone induces an acute facilitory effect on GnRH-induced LH and FSH secretion which is estrogen-dependent.
Effects of decreasing the frequency of gonadotropin-releasing hormone stimulation on gonadotropin secretion in gonadotropin-releasing hormone-deficient men and perifused rat pituitary cells.