Okatani Y, Morioka N, Hayashi K
Department of Obstetrics and Gynecology, Kochi Medical School, Oko, Nankoku, Kochi, Japan.
J Pineal Res. 1999 Sep;27(2):65-72. doi: 10.1111/j.1600-079x.1999.tb00598.x.
To evaluate changes in melatonin synthesis during the perimenopausal period in the female rat and to determine the effects of estrogen on melatonin synthesis, pineal levels of tryptophan, melatonin and norepinephrine and activities of N-acetyltransferase (NAT) and hydroxyindole-O-methyltransferase (HIOMT) were determined. Homogenates for assay were prepared from the pineal glands of female virgin Sprague-Dawley rats between 4 and 24 months of age in the middle of the dark period of a daily light/dark cycle. Serum 17 beta-estradiol (E2) concentrations were also determined. Pineal melatonin levels significantly decreased from month 4 12 and significantly increased from month 12 16, decreasing thereafter. Serum E2 concentrations significantly decreased from month 12-16, and remained low thereafter. No significant changes in tryptophan or norepinephrine were seen. NAT activities paralleled the time course of changes in melatonin. HIOMT activities decreased gradually from month 4 24. Subcutaneous implantation of an E2 capsule between months 12 and 16 resulted in significant decreases in levels of melatonin and NAT activity at month 16. Ovariectomy at month 4 or 12 led to significant increases in the levels of melatonin and NAT activity. These findings represent a temporal increase in pineal melatonin synthesis during the perimenopausal period, and suggest that the increase in melatonin synthesis activity at that time might result from decreasing levels of endogenous estrogen. The effect of estrogen on melatonin synthesis appeared to involve modulation of NAT activity.
为评估雌性大鼠围绝经期褪黑素合成的变化，并确定雌激素对褪黑素合成的影响，测定了松果体中色氨酸、褪黑素和去甲肾上腺素的水平以及N - 乙酰转移酶（NAT）和羟基吲哚 - O - 甲基转移酶（HIOMT）的活性。用于检测的匀浆取自4至24月龄处于日常明暗周期黑暗期中间的雌性未孕Sprague - Dawley大鼠的松果体。还测定了血清17β - 雌二醇（E2）浓度。松果体褪黑素水平在4至12个月时显著下降，在12至16个月时显著升高，此后下降。血清E2浓度在12至16个月时显著下降，此后保持在低水平。色氨酸或去甲肾上腺素未见显著变化。NAT活性与褪黑素变化的时间进程平行。HIOMT活性从4至24个月逐渐下降。在12至16个月间皮下植入E2胶囊导致16个月时褪黑素水平和NAT活性显著下降。在4或12个月时进行卵巢切除导致褪黑素水平和NAT活性显著升高。这些发现表明围绝经期松果体褪黑素合成有一个暂时的增加，并且提示此时褪黑素合成活性的增加可能是由于内源性雌激素水平降低所致。雌激素对褪黑素合成的影响似乎涉及对NAT活性的调节。
