Effect of exogenous gonadotropins on gonadotrophs of the rat pituitary gland

In the human in vitro fertilization (IVF) program a variety of superovulati on regimens have been employed to promote follicular stimulation and the re cruitment of supernumerary oocytes. This therapy, however, disturbs serum c oncentrations of estradiol and progesterone and may disrupt the normal feed back systems of the hypothalamo-pituitary axis. This study examines the eff ects of hyperstimulation on the pituitary gonadotrophs and circulating gona dotrophins. FSH and human chorionic gonadotropin (hCG) were administered to normal cycl ing female Sprague-Dawley rats (n = 12) in phase with their estrous cycle. Control rats (n = 12) were injected with saline. In both the experimental a nd control groups, six rats were mated on the evening of proestrus and kill ed 12 hr later, while six animals were killed prior to mating. Blood was co llected at the time of sacrifice for radioimmunoassay. The pituitary glands were removed, processed for light microscopy and serially sectioned. Immun ocytochemistry for LH and FSH was carried out to determine the area occupie d by these cell types. Data were statistically analyzed. Findings were corr elated with circulating levels of LH, FSH, estradiol and progesterone. RIA revealed that the concentration of LH, FSH, estradiol and progesterone mere significantly different with respect to hyperstimulation and mating. In ad dition the area occupied by LH and FSH cells was significantly different wi th respect to both hyperstimulation and mating. Hyperstimulation affects gonadotroph content, as well as gonadotropin and s ex steroid hormone concentrations and together with other factors, may disr upt the ideal environment required for implantation. Anat Rec 254:367-374, 1999. (C) 1999 Wiley-Liss, Inc.