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首页> 外文期刊>Journal of neuroendocrinology >Chronic exposure to low levels of oestradiol-17beta affects oestrous cyclicity, hypothalamic norepinephrine and serum luteinising hormone in young intact rats.
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Chronic exposure to low levels of oestradiol-17beta affects oestrous cyclicity, hypothalamic norepinephrine and serum luteinising hormone in young intact rats.

机译：长期暴露于低水平的雌二醇17β会影响完整的幼鼠的雌性周期性，下丘脑去甲肾上腺素和血清黄体生成激素。

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Chronic exposure to oestrogens is known to inhibit the secretion of luteinising hormone (LH) in rats, leading to anovulation. Hypothalamic catecholamines, norepinephrine and dopamine play an important role in LH regulation. However, the effects of chronic exposure to low levels of oestradiol on hypothalamic catecholamines have not been investigated thoroughly. In the present study, adult female Sprague-Dawley rats were either sham implanted or implanted with 17beta-oestradiol (E(2)) pellets (20 ng/day) for 30 (E-30), 60 (E-60) or 90 (E-90) days. E(2) exposure affected oestrous cyclicity and ovarian morphology in a duration-dependent manner. There was no change in oestrous cyclicity in E-30 rats; however, 75% of E-60 and 95% of E-90 rats were acyclic (P < 0.05). Cycling rats from E-30 or the control group were killed at different time points on the afternoon of pro-oestrous. E-30 rats in oestrous, constant oestrous rats in the E-60 and E-90 groups and a group of old constant oestrous (OCE) rats were killed at 12.00 h. LH was measured in the serum by radioimmunoassay. Individual hypothalamic nuclei that are involved in LH regulation were microdissected and analysed for norepinephrine and dopamine levels using high-performance liquid chromatography/electrochemical detection. Norepinephrine levels in the hypothalamic nuclei increased significantly in control and E-30 groups during the afternoon of pro-oestrous, which was accompanied by a rise in LH levels (P < 0.05). On the day of oestrous, norepinephrine concentrations in hypothalamic nuclei and serum LH were significantly lower in E-60, E-90 and OCE rats compared to E-30 and control rats. On the other hand, dopamine levels declined significantly in one hypothalamic nucleus. These results indicate that chronic E(2) exposure affects hypothalamic catecholamine and serum LH levels in a duration-dependent manner. This coincides well with the loss of cyclicity observed in these animals. These results suggest that repeated exposure to endogenous oestrogens could play a role in reproductive senescence.
机译：已知长期暴露于雌激素会抑制大鼠黄体生成激素（LH）的分泌，从而导致无排卵。下丘脑儿茶酚胺，去甲肾上腺素和多巴胺在LH调节中起重要作用。然而，尚未充分研究长期暴露于低水平的雌二醇对下丘脑儿茶酚胺的影响。在本研究中，成年雌性Sprague-Dawley大鼠被假植入或用17β-雌二醇（E（2））药丸（20 ng /天）植入30（E-30），60（E-60）或90 （E-90）天。 E（2）暴露以持续时间依赖的方式影响雌激素循环和卵巢形态。 E-30大鼠的雌激素循环没有改变;然而，E-60大鼠中有75％和E-90大鼠中有95％是无环的（P <0.05）。 E-30或对照组的骑自行车大鼠在促发性下午的不同时间点处死。 E-12和E-90组的雌性恒定雌性大鼠中的E-30大鼠和一组老的恒定雌性（OCE）大鼠在12.00 h处死。通过放射免疫测定法测定血清中的LH。显微解剖涉及LH调节的单个下丘脑核，并使用高效液相色谱/电化学检测分析去甲肾上腺素和多巴胺水平。对照和E-30组在下雌激素后的下午，下丘脑核中去甲肾上腺素水平显着增加，同时伴随着LH水平的升高（P <0.05）。在发情的那天，与E-30和对照组相比，E-60，E-90和OCE大鼠的下丘脑核中去甲肾上腺素浓度和血清LH显着降低。另一方面，一个下丘脑核中的多巴胺水平显着下降。这些结果表明，慢性E（2）暴露以持续时间依赖性的方式影响下丘脑儿茶酚胺和血清LH水平。这与在这些动物中观察到的周期性丧失恰好吻合。这些结果表明，反复接触内源性雌激素可能在生殖衰老中起作用。

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