The Effect of Ovariectomy on The Secretion of Follicle Stimulating Hormone ( FSH ) and mRNA Levels of FSHbeta subunit in Rat / 대한산부인과학회잡지

ABSTRACT

Follicle stmulating hormone ( FSH ) consist of alpha and beta subunits, which are encoded by se-parate genes. Pituitary release of FSH appears to be regulated by the hypothalamic GnRH and the gonadal steroid hormones. In addition, inhibin and follistatin produced by the gonad have been known to inhibit FSH secretion selectively. However, little is known about their regulation of the biosynthesis of FSH subunits at transcriptional and posttranscriptional levels. In the pre-sent study, we studied the time course of changes in alpha and FSH beta subunit mRNA concentrati-ons after castration and the effects of ovarian steroids of changes in alpha and FSH beta subunit mRNA concentrations after castration and the effects of ovarian steroids on alpha and FSH beta subunit mRNA in ovariectomized rats in order to determine Whether FSH subunit synthesis is modulated at the pretranslational levels, and whether synthesis and secretion are differently regulated. Results are as follows 1. The time course of the rise in the steady state alpha subunit and FSH beta subunit mRNA levels were observed after ovariectomy, which paralleled the increases in serum and pituitary FSH concentrations. The time course experiments revealed differences in the patterns of alpha and FSH beta subunit mRNA responses, the rise in FSH beta subunit mRNA levels being more pro- minent than the rise in alpha subunit mRNA. 2. FSH beta mRNA levels were negatively regulated by the single injection of progesterone but not by estradiol, suggesting that FSH beta subunit mRNA seemed to be more sensitive to ne-gative feedback by progesterone than estradiol. Similar results were obtained by the continuous treatment of ovarian steroids for 1~4 days, but inhibition was more prominent with continuous treatment. It is, therefore, concluded that estradiol and progesterone inhibit the synthesis of FSH at the pretranslational level by modulating the steady state levels of alpha and FSH beta subunit mRNA, progesterone effect being more promiment than that of estradiol and alpha and FSH beta subunit are regulated in a different manner.