Grattan D R, Averill R L
Animal Physiology Research Unit, School of Biological Sciences, Victoria University of Wellington, New Zealand.
Endocrinology. 1990 Feb;126(2):1199-205. doi: 10.1210/endo-126-2-1199.
PRL secretion in several physiological and experimental conditions, including early pregnancy, is linked to the daily photoperiod. The aim of this study was to examine the antepartum increase in PRL secretion for evidence of a circadian pattern of release, as seen during early pregnancy. During the last 3 days of pregnancy blood samples were taken six times daily by means of previously implanted jugular cannulae. Plasma PRL concentrations were then measured by RIA. PRL levels were less than 10 ng/ml in all animals on day 19 of pregnancy, but during the light period of day 20 there was an increase to an average of 30 +/- 10 ng/ml, with no evidence of a peak related to the time of day. However, in the dark period between days 20 and 21 there was a large surge of PRL secretion which reached peak levels of 356 +/- 39 ng/ml at 0500 h on day 21, then returned to 48 +/- 20 ng/ml at 1200 h, around the time of parturition. The peak always occurred at 0500 h and was not related to the time of parturition which ranged from 1000-2200 h on day 21. Bilateral ovariectomy (OVX) on day 19 advanced the time of delivery by approximately 12 h. In seven of nine animals, no surge of PRL secretion was observed during the dark period preceding parturition. Estradiol treatment after OVX on day 19 (OVX+E) advanced the time of delivery by approx 18 h. An antepartum PRL surge was present and was advanced by 24 h in all OVX+E animals, peaking at 0300 h on day 20. Progesterone treatment from day 18 to 21 in intact pregnant animals delayed parturition by approximately 18 h and prevented PRL secretion during the period of treatment. After progesterone treatment was stopped, a nocturnal surge of PRL secretion occurred, peaking at 0500 h on day 22, 24 h after the surge in normal animals. The results suggest that the increased PRL secretion during late pregnancy is linked to the daily photoperiod and is characterized by a nocturnal surge in the dark period preceding parturition. This surge is inhibited by progesterone, and it can be advanced 24 h by estradiol treatment in the absence of the ovaries.
在包括妊娠早期在内的多种生理和实验条件下，催乳素（PRL）的分泌与每日光照周期有关。本研究的目的是检查产前PRL分泌的增加情况，以寻找如妊娠早期所见的昼夜节律性释放的证据。在妊娠的最后3天，通过先前植入的颈静脉插管每天采集6次血样。然后通过放射免疫分析（RIA）测定血浆PRL浓度。在妊娠第19天，所有动物的PRL水平均低于10 ng/ml，但在第20天的光照期间，PRL水平升高至平均30±10 ng/ml，未发现与一天中的时间相关的峰值。然而，在第20天和第21天之间的黑暗期，PRL分泌大幅激增，在第21天05:00时达到峰值水平356±39 ng/ml，然后在分娩前后的12:00时降至48±20 ng/ml。峰值总是出现在05:00时，与第21天10:00至22:00之间的分娩时间无关。在第19天进行双侧卵巢切除术（OVX）使分娩时间提前约12小时。在9只动物中的7只中，在分娩前的黑暗期未观察到PRL分泌激增。在第19天进行OVX后给予雌二醇治疗（OVX+E）使分娩时间提前约18小时。所有OVX+E动物均出现产前PRL激增，且提前24小时，在第20天03:00时达到峰值。在完整的妊娠动物中，从第18天至21天给予孕酮治疗使分娩延迟约18小时，并在治疗期间阻止PRL分泌。停止孕酮治疗后，出现夜间PRL分泌激增，在第22天05:00时达到峰值，比正常动物的激增时间晚24小时。结果表明，妊娠后期PRL分泌增加与每日光照周期有关，其特征是在分娩前的黑暗期出现夜间激增。这种激增受到孕酮的抑制，在没有卵巢的情况下，通过雌二醇治疗可使其提前24小时。
