Interaction Between Oestrogen and Gonadotrophin-Releasing Hormone on the Release and Synthesis of Luteinizing Hormone and Follicle-Stimulating Hormone From Incubated Pituitaries

Abstract

The release and synthesis of LH and FSH were studied in adenohypophyses from ovariectomized rats incubated for a period of 4 h in flasks containing 1 ml Eagle's medium. One hemipituitary was used as the experimental gland and the other half served as a control. Glands from ovariectomized untreated animals showed a spontaneous release of LH and FSH and the amount of hormones released (per mg gland) by both the hemipituitaries was not significantly different. Also the content of the hormones at the end of the incubation period was similar in both halves. Gonadotrophin-releasing hormone (Gn-RH) added to the incubation medium stimulated the release of LH and FSH. A dose--response relationship was obtained between doses of 0-51 and 8-00 ng/ml medium. Although lower doses were required to increase the release of LH, the amount of FSH released was higher when expressed as a percentage of gland content. Pituitary glands from ovariectomized rats treated with 5 mug oestradiol benzoate 24 h before being killed showed an increase in sensitivity to Gn-RH, but the response decreased when oestrogen was injected 2 h before death. Also the addition of oestradiol-17beta to the incubation medium inhibited LH and FSH release induced by Gn-RH. Gonadotrophin-releasing hormone increased the spontaneous synthesis of LH and FSH observed in the incubated pituitaries. This effect of Gn-RH was stimulated by the injection of oestrogen into the donor animals whereas administration of oestrogen into the medium enhanced the synthesis of LH and partially inhibited that of FSH. These results provide evidence for a dual effect of oestrogen on the release of LH and FSH induced by Gn-RH. They also show that synthesis of gonadotrophic hormones was favoured by oestrogen or by increased gonadotrophin release.

GnRH-Stimulated Glycosylation (Proximal and Distal) of Luteinizing Hormone by Cultured Rat Pituitary Cells

“…As in our previous works [4,9], addition of GnRH into the incubation medium was fol lowed by time-related increases in total content of iLH (cells plus medium), these being significantly higher than control at 4 h (116%) and 5 h (118%; fig. 1 …”

Different effects of inhibitors of protein synthesis on the inhibited and augmented LH response of pituitary glands from ovariectomized rats to LH‐RH in vitro after pretreatment with oestradiol‐17β‐benzoate in vivo

“…Neither the negative nor the positive phase are the result of changes in pituitary LH content [1,16]. Although it has been found that oestrogen pretreatment of pituitary glands may stimulate synthesis of LH [17], our results demonstrate that LH synthesis is not obligatory for the development of the positive phase. However, further maturation of the LH polypeptide chains to the glycoprotein molecule still might play a role [18].…”

2,3,7,8-Tetrachlorodibenzo-p-dioxin potentially attenuates the gene expression of pituitary gonadotropin .BETA.-subunits in a fetal age-specific fashion: a comparative study using cultured pituitaries

“…In accordance with above pieces of information, the concentrations of serum and pituitary FSH in male fetuses are lower compared with female fetuses (Aubert et al, 1985;McNamara et al, 1985;Granz et al, 1997;Takeda et al, 2009). Furthermore, the magnitude of stimuli-induced FSH synthesis is lesser than that of LH synthesis, and the turnover rate of FSH is greater than that of LH (Apfelbaum and Taleisnik, 1976;Muyan et al, 1994). Such differences in expression between LH and FSH seem to explain the sex difference of the GnRH-or cAMP-mediated induction of FSHβ and the TCDD effects on them.…”