흰쥐의 뇌하수체 전엽배양세포에 gonadotropin-releasing hormone (GnRH)을 처리하였을 때 시간이 경과함에 따라 GnRH농도에 비례하여 luteinizing hormone(LH)의 분비가 증가하였으며, 2시간까지 급격하게 증가하였다. 또한 GnRH를 처리하였을때 α subunit mRNA의 농도는 증가하지 않았으나 LHβ subunit mRNA의 농도는 GnRH 농도에 비례하여 증가하였으며, GnRH 처리후 6시간 이후부터 유의하게 증가하였다. 특히 최종농도가 2 × 10-10M이 되도록 GnRH를 처리하였을 때 LHβ subunit mRNA 농도가 2.7배 정도 최대로 증가하였다. 또한 estradiol을 단독으로 또는 GnRH와 동시에 처리하였을때 LH분비가 증가하지 않았으나 progesterone을 GnRH와 동시에 처리하였을때 LH분비가 유의하게 증가하였다. 또한 LHβ subunit mRNA의 농도는 estradiol및 progesterone을 단독으로 또는 GnRH와 동시에 처리하였을때 난소호르몬 농도에 의존적으로 LHβ subunit mRNA의 농도가 증가하였다. Estradiol에 의한 LHβ subunit mRNA의 증가양상은 estrogen 길항제인 LY117018에 의하여 유의하게 감소하였다. 이러한 결과로 보아 GnRH는 steady state LHβ subunit mRNA 농도에 영향을 미치므로써 LH분비 및 LH subunit 생합성을 조절하며 난소호르몬은 뇌하수체에 직접 작용하여 LH분비 및 LH subunit 생합성에 영향을 주는 것으로 보인다.
The effects of gonadoropin-releasing hormone (GnRH) and ovarian steroid hormones on the release of luteinizing hormone (LH) and its subunit mRNA levels were investigated in anterior pituitary cells in culture. LH concentration was measured by a specific radioimmunoassay and mRNA levels of u and LHβ subunits by RNA slot blot hybridization assay. GnRH stimulated LH release in a dose-dependent manner from cultured pituitary cells. However, the basal LH release in the absence of GnRH was not changed during the course of 24h culture, strongly suggesting that release of LH is directly controlled by GnRH. The treatment of the pituitary cells with GnRH increased LHβ subunit mRNA levels in a dose-dependent manner, reaching the maximum with 2 × 10-10M GnRH while no significant increase in α subunit mRNA levels was observed after GnRH treatment. Estradiol did not augment GnRH-induced LH release while progesterone augmented GnRH-induced LH release in a dose-dependent manner at the level of pituitary. However, estradiol and progesterone increased basal and GnRH-induced LHβ subunit mRNA levels in a dose-dependent manner. The treatment of estrogen antagonist, LYI17018 blocked the effect of estradiol on GnRH-induced LHβ subunit mRNA levels in a dose-dependent manner while progesterone antagonist, Ru486 tended to block the effect of progesterone on GnRH-induced LHβ subunit mRNA levels. It is therefore suggested that GnRH Playa a major role in LH release and subunit biosynthesis by influencing the steady state LHβ subunit mRNA loves and ovarian steroid hormones modulate subunit biosynthesis via directly acting on pituitary gonadotropes.
