Haisenleder D J, Ortolano G A, Landefeld T D, Zmeili S M, Marshall J C
Department of Internal Medicine and Pharmacology, University of Michigan, Ann Arbor 48109.
Endocrinology. 1989 Apr;124(4):2023-8. doi: 10.1210/endo-124-4-2023.
Pituitary PRL mRNA concentrations were measured during the 4-day rat estrous cycle. Adult female Sprague-Dawley rats were killed at 3-h intervals throughout the cycle and hourly between 1000 and 2400 h on proestrus (n = 5-12). Serum PRL was increased on the afternoons of proestrus (P) and estrus (E), with peak concentrations at 1700 h (P, 624 +/- 126; E, 261 +/- 107 ng/ml). PRL mRNA concentrations were elevated during the evening on P and E (2300 h: P, 14.4 +/- 1.5; E, 16.1 +/- 1.3 ng cDNA bound/100 micrograms pituitary DNA) to values 2-fold higher than those at 0800 h on each respective day. On diestrus (D) PRL mRNA levels decreased abruptly during the morning (1100 h, 1.7 +/- 0.3 ng cDNA bound), followed by a 6- to 7-fold increase between 1700 and 2000 h on the same evening. In contrast, PRL mRNA levels were elevated at 0800 h on metestrus (M). The changes in PRL mRNA concentrations obtained on M and D were not associated with increased PRL secretion. A more detailed examination of P revealed that PRL mRNA levels increased during the morning (1000 h, 9.9 +/- 2.6 ng cDNA bound), then decreased abruptly at 1100 h (4.9 +/- 1.2). The morning rise in mRNA concentrations was followed by a 2-fold rise in pituitary PRL content. As serum PRL rose during the afternoon surge, a coincident decrease in pituitary PRL content and an increase in PRL mRNA levels were observed. The relationship between PRL secretion and gene expression was further examined in ovariectomized estradiol-replaced rats receiving either bromocriptine (1.2 mg/day, sc) or vehicle control sc. The vehicle-treated group expressed a characteristic afternoon PRL surge between 1500 and 2100 h. Pituitary PRL decreased during the surge to 10% of morning values, and PRL mRNA levels increased 2-fold beginning 2 h after initiation of the surge. These changes in serum PRL, pituitary PRL, and PRL mRNA levels were abolished by bromocriptine administration. These data reveal that alterations in PRL mRNA concentrations occur on a daily basis during the rat estrous cycle. Increases occur during the evenings of P and E at the time of the increase in PRL secretory activity. The effect of blocking the PRL surge in ovariectomized estradiol-replaced rats suggests a regulatory interaction between secretion and gene expression.(ABSTRACT TRUNCATED AT 250 WORDS)
在大鼠4天的发情周期中测量垂体催乳素（PRL）mRNA浓度。成年雌性Sprague-Dawley大鼠在整个周期中每隔3小时处死一批，在发情前期（n = 5 - 12）的10:00至24:00每小时处死一批。发情前期（P）和发情期（E）下午血清PRL升高，17:00浓度达到峰值（P期，624±126；E期，261±107 ng/ml）。PRL mRNA浓度在发情前期和发情期的晚上升高（23:00：P期，14.4±1.5；E期，16.1±1.3 ng cDNA结合/100μg垂体DNA），比各自当天08:00时的值高2倍。在间情期（D），PRL mRNA水平在上午（11:00，1.7±0.3 ng cDNA结合）突然下降，随后在同一天晚上17:00至20:00之间增加6至7倍。相比之下，在发情后期（M）的08:00时PRL mRNA水平升高。在发情后期和间情期获得的PRL mRNA浓度变化与PRL分泌增加无关。对发情前期更详细的检查显示，PRL mRNA水平在上午（10:00，9.9±2.6 ng cDNA结合）升高，然后在11:00时突然下降（4.9±1.2）。mRNA浓度上午升高后，垂体PRL含量增加2倍。随着下午血清PRL升高，观察到垂体PRL含量同时下降和PRL mRNA水平增加。在接受溴隐亭（1.2 mg/天，皮下注射）或载体对照皮下注射的去卵巢并补充雌二醇的大鼠中，进一步研究了PRL分泌与基因表达之间的关系。载体处理组在15:00至21:00之间出现典型的下午PRL激增。激增期间垂体PRL降至上午值的10%，PRL mRNA水平在激增开始2小时后开始增加2倍。溴隐亭给药消除了血清PRL、垂体PRL和PRL mRNA水平的这些变化。这些数据表明，在大鼠发情周期中，PRL mRNA浓度每天都发生变化。在发情前期和发情期晚上PRL分泌活动增加时出现升高。在去卵巢并补充雌二醇的大鼠中阻断PRL激增的作用表明分泌与基因表达之间存在调节相互作用。（摘要截短至250字）
