Downing S J, Sherwood O D
Endocrinology. 1985 Mar;116(3):1206-14. doi: 10.1210/endo-116-3-1206.
In control intact rats (group C), the frequency of intrauterine pressure cycles (IUPC) declines steadily during pregnancy from 80-130 cycles/3 h on day 10 (D10) to 20-30 cycles/3 h on D20. The decline in frequency is due to increasingly prolonged periods of myometrial quiescence, which increase from 30-90 min/3 h on D10 to 120-150 min/3 h by D20. During the 24 h preceding labor, the frequency of IUPC remains at less than 15 cycles/h until 3 h prepartum, when there is an abrupt increase to 30 cycles/h. Ovariectomized pregnant animals treated with progesterone (P) and estrogen (E; group OPE) exhibit significantly greater frequency of IUPC and significantly lower incidence of myometrial quiescence than intact pregnant rats from D12 and for the remainder of pregnancy. Ovariectomized pregnant rats that received P, E, and porcine relaxin (R: group OPER) or P and porcine R only (group OPR) exhibited declining frequency of IUPC similar to that observed in group C animals. Group OPER rats exhibited prolonged periods of myometrial quiescence of similar duration to those observed in control intact rats. In group OPR animals, however, the periods of myometrial quiescence were considerably diminished during late pregnancy. Group OPER animals exhibited a pattern of myometrial activity during labor and postpartum similar to that of control animals. The results suggest an important role for R in the control of myometrial activity during the second half of pregnancy and parturition in the rat.
在对照未处理的大鼠（C组）中，妊娠期间子宫内压周期（IUPC）的频率从第10天（D10）的80 - 130次/3小时稳步下降至第20天的20 - 30次/3小时。频率下降是由于子宫肌层静止期越来越长，其从D10的30 - 90分钟/3小时增加至D20的120 - 150分钟/3小时。在分娩前24小时内，IUPC频率保持在15次/小时以下，直到产前3小时，此时突然增加到30次/小时。用孕酮（P）和雌激素（E；OPE组）处理的去卵巢妊娠动物，从D12开始及在妊娠剩余时间内，其IUPC频率显著更高，子宫肌层静止的发生率显著更低。接受P、E和猪松弛素（R：OPER组）或仅接受P和猪R（OPR组）的去卵巢妊娠大鼠，其IUPC频率下降情况与C组动物相似。OPER组大鼠子宫肌层静止期延长，时长与对照未处理大鼠相似。然而，在OPR组动物中，妊娠后期子宫肌层静止期显著缩短。OPER组动物在分娩和产后子宫肌层活动模式与对照动物相似。结果表明，R在大鼠妊娠后半期和分娩期间子宫肌层活动的控制中起重要作用。
