Haisenleder D J, Ortolano G A, Dalkin A C, Ellis T R, Paul S J, Marshall J C
Department of Internal Medicine, University of Michigan, Ann Arbor 48109.
Endocrinology. 1990 Dec;127(6):2869-75. doi: 10.1210/endo-127-6-2869.
The role of GnRH in regulating gonadotropin subunit gene expression was examined in adult female rats. Animals were ovariectomized, estradiol implants inserted sc, and jugular cannulae placed into the right atria. On the next day, animals were given GnRH pulses (saline to controls) every 30 min for up to 48 h and alpha, LH beta, and FSH beta mRNA levels measured by hybridization to cDNA probes. To determine the effects of GnRH treatment duration, rats received GnRH pulses (25 ng at 30-min intervals) for 6, 12, 24, and 48 h. FSH beta mRNA was increased (by 92%) after 6 h of pulses and remained elevated through 48 h. alpha mRNA was not increased until 12 h (27% increase) and rose further (57%) by 48 h. LH beta mRNA levels were only transiently increased at 12 h (67%) and values were not different from saline controls after 24 or 48 h. To examine whether the rise in serum PRL which is characteristic of the ovariectomized-estradiol animal model was responsible for the decrease in LH beta mRNA responsiveness to GnRH over longer durations, studies were repeated in bromocriptine-treated animals (0.6 mg sc, twice daily). The results showed similar response patterns for all three subunit mRNAs including the decrease in LH beta after 48 h. A third experiment examined the effect of varying GnRH pulse amplitude (0.5-250 ng/pulse at 30-min intervals) over 12 h. alpha mRNA levels were increased by all GnRH doses greater than 5 ng with maximum responses after 250 ng pulses. LH and FSH beta mRNAs were both elevated by GnRH pulse doses of 0.5-25 ng (P less than 0.05 vs. saline controls). Maximal increases (2-fold) were seen after 5 ng pulses for LH beta and after 15-ng pulses for FSH beta mRNA. These results show that pulsatile GnRH increases FSH beta mRNA more rapidly than alpha or LH beta mRNAs in female rats. In addition, high amplitude GnRH pulses increase only alpha mRNA, whereas both LH beta and FSH beta mRNAs show maximum responses to lower doses. The data suggest that alterations in the amplitude of the GnRH pulsatile signal can exert differential effects on gonadotropin gene expression.
在成年雌性大鼠中研究了促性腺激素释放激素（GnRH）在调节促性腺激素亚基基因表达中的作用。将动物进行卵巢切除，皮下植入雌二醇，在右心房置入颈静脉插管。次日，每30分钟给动物注射GnRH脉冲（给对照组注射生理盐水），持续48小时，通过与cDNA探针杂交来测定α、促黄体生成素β（LHβ）和促卵泡生成素β（FSHβ）的mRNA水平。为了确定GnRH治疗持续时间的影响，大鼠接受GnRH脉冲（每隔30分钟25 ng），持续6、12、24和48小时。脉冲6小时后FSHβ mRNA增加（增加92%），并在48小时内持续升高。α mRNA直到12小时才增加（增加27%），48小时时进一步升高（增加57%）。LHβ mRNA水平仅在12小时时短暂增加（增加67%），24或48小时后其值与生理盐水对照组无差异。为了研究在去卵巢 - 雌二醇动物模型中特征性的血清催乳素升高是否是导致LHβ mRNA对GnRH的反应性在较长时间内下降的原因，在接受溴隐亭治疗的动物（皮下注射0.6 mg，每日两次）中重复进行研究。结果显示所有三种亚基mRNA的反应模式相似，包括48小时后LHβ的下降。第三个实验研究了在12小时内改变GnRH脉冲幅度（每隔30分钟0.5 - 250 ng/脉冲）的影响。所有大于5 ng的GnRH剂量均可使α mRNA水平升高，250 ng脉冲后出现最大反应。GnRH脉冲剂量为0.5 - 25 ng时，LHβ和FSHβ mRNA均升高（与生理盐水对照组相比，P < 0.05）。LHβ mRNA在5 ng脉冲后出现最大增加（增加2倍），FSHβ mRNA在15 ng脉冲后出现最大增加（增加2倍）。这些结果表明，在雌性大鼠中，脉冲式GnRH增加FSHβ mRNA的速度比α或LHβ mRNA更快。此外，高幅度GnRH脉冲仅增加α mRNA，而LHβ和FSHβ mRNA对较低剂量表现出最大反应。数据表明，GnRH脉冲信号幅度的改变可对促性腺激素基因表达产生不同影响。
