Okatani Y, Hayashi K, Watanabe K, Morioka N, Sagara Y
Department of Obstetrics and Gynecology, Kochi Medical School, Japan.
J Pineal Res. 1998 Mar;24(2):67-72. doi: 10.1111/j.1600-079x.1998.tb00368.x.
Our objective was to evaluate the effect of estrogen on the synthesis of melatonin in female rats during the peripubertal period. The level of melatonin and of N-acetyl serotonin (NAS) and the activity of N-acetyltransferase (NAT) and of hydroxy-indole-O-methyltransferase (HIOMT) were determined in homogenates of pineal glands from peripubertal female Sprague-Dawley rats in the mid-dark during the daily light/dark cycle between 4 and 10 weeks of age. Ovariectomy was performed and daily administration of estradiol benzoate (E2B) was initiated at 6 weeks of age. A peak in the pineal level of melatonin and NAS and in NAT activity was observed in untreated (control) rats with intact ovaries at 6 weeks. Thereafter, HIOMT activity increased and remained unchanged. Ovariectomy at week 6 led to significant increases in the level of melatonin and of NAS and in NAT activity at week 8. At week 10, NAT activity was similar to that of control animals, but melatonin and NAS levels were slightly elevated. Ovariectomy did not affect HIOMT activity. The subcutaneous injection of a low dose (0.1 microg/day) of E2B suppressed the ovariectomy-induced elevation of levels of melatonin and NAS and of NAT activity, similar to that seen in rats with intact ovaries. A higher dose of E2B (1.0 microg/day) reduced the activity of NAT and HIOMT to values significantly below the control values. Results suggest that estrogen modulates the nocturnal synthesis of melatonin by the pineal gland in peripubertal female rats. The decline in melatonin synthesis during puberty may be related to an increase in the estrogen level. The inhibitory effect of estrogen in melatonin synthesis appeared to be mediated by the modulation of NAT activity.
我们的目的是评估雌激素对青春期前后雌性大鼠褪黑素合成的影响。在4至10周龄的雌性斯普拉格-道利大鼠青春期前后，于日常光照/黑暗周期的午夜期间，测定其松果体匀浆中褪黑素、N-乙酰血清素（NAS）的水平以及N-乙酰转移酶（NAT）和羟基吲哚-O-甲基转移酶（HIOMT）的活性。在6周龄时进行卵巢切除术，并开始每日注射苯甲酸雌二醇（E2B）。在6周龄时，未处理（对照）的完整卵巢大鼠的松果体中褪黑素和NAS水平以及NAT活性出现峰值。此后，HIOMT活性增加并保持不变。6周时进行卵巢切除术导致8周时褪黑素和NAS水平以及NAT活性显著增加。在10周时，NAT活性与对照动物相似，但褪黑素和NAS水平略有升高。卵巢切除术不影响HIOMT活性。皮下注射低剂量（0.1微克/天）的E2B可抑制卵巢切除术后褪黑素和NAS水平以及NAT活性的升高，与完整卵巢大鼠的情况相似。较高剂量的E2B（1.0微克/天）可使NAT和HIOMT的活性降低至显著低于对照值。结果表明，雌激素可调节青春期前后雌性大鼠松果体夜间褪黑素的合成。青春期褪黑素合成的下降可能与雌激素水平的升高有关。雌激素对褪黑素合成的抑制作用似乎是通过调节NAT活性介导的。
