Fuchs A R, Ivell R, Ganz N, Fields M J, Gimenez T
Department of Obstetrics and Gynecology, Weill Medical College of Cornell University, New York, New York 10021, USA.
Biol Reprod. 2001 Oct;65(4):1135-41. doi: 10.1095/biolreprod65.4.1135.
Plasma oxytocin (OT) concentrations were determined in 14 late-pregnant and parturient Angus-Hereford cows. Jugular and utero-ovarian veins were cannulated for simultaneous withdrawal of blood samples. Samples were collected at 10-min intervals for 6 h once weekly beginning 60-14 days before the date of expected delivery (group 1), or daily 3-7 days before the due date (group 2). In a third group, samples were collected at 15-min intervals every other day for 12 h beginning 1 wk before calving. Basal levels of OT were low, the overall mean for both veins was 0.46 +/- 0.03 microU/ml until a week before parturition, and then increased to 0.77 +/- 0.1 microU/ml (P < 0.02). Spurts of OT occurred intermittently on all days. Interpeak intervals averaged 71.0 +/- 10.7 min until Day -14, and from Day -14 to Day -1 the intervals were 44.0 +/- 5.3 min (P < 0.05). From Day -60 to Day -25 the amplitudes of OT peaks were low and similar in both veins (mean 1.37 +/- 0.1 microU/ml). From Day -14 to Day -1 the peak amplitudes were 3.6 +/- 0.4 microU/ml on average (P < 0.02). During the last 2 wk the utero-ovarian peak of OT was frequently higher than the peripheral peak. In addition, a number of spurts were observed in the utero-ovarian vein only (solo peaks). On the day of parturition during the first stage of labor, peak amplitudes had increased to 7.3 +/- 2.0 microU/ml, and the interpeak intervals had become shorter than before labor (mean 25.1 +/- 2.6 min). A large surge of OT initiated the expulsive stage of labor. Basal levels rose to 43.1 +/- 16 microU/ml and 38.7 +/- 12.6 microU/ml, and peak levels to 77.4 +/- 19.1 microU/ml and 91.6 +/- 21 microU/ml in the jugular and utero-ovarian veins, respectively. Interpeak intervals had decreased to 17.2 +/- 3.3 min (P < 0.05). Oxytocin levels remained high after delivery of the calf until the placenta was expelled. The posterior pituitary was the source of circulating OT during most of gestation and labor, but the solo peaks observed during late gestation in the utero-ovarian vein were probably of luteal origin or possibly of caruncular origin, because near term, both tissues express OT mRNA. Fetal posterior pituitary is another possible source for these peaks. Our conclusions are that during bovine pregnancy, low amplitude spurts of OT are secreted intermittently; near term, both the frequency and peak amplitude of the spurts increase; and during labor, a dramatic increase in plasma OT precedes the expulsion of the calf. The main source of OT is the posterior pituitary, but near term, a utero-ovarian source secretes additional OT into the systemic circulation.
对14头怀孕后期及分娩期的安格斯-赫里福德母牛测定了血浆催产素（OT）浓度。通过插管颈静脉和子宫卵巢静脉同时采集血样。从预计分娩日期前60 - 14天开始，每周一次，以10分钟的间隔采集样本6小时（第1组）；或者在预产期前3 - 7天每天采集（第2组）。在第三组中，从分娩前1周开始，每隔一天以15分钟的间隔采集样本12小时。OT的基础水平较低，在分娩前一周前，两条静脉的总体平均值为0.46±0.03微单位/毫升，然后升至0.77±0.1微单位/毫升（P<0.02）。OT的峰值在所有日子里间歇性出现。直到第 - 14天，峰值间隔平均为71.0±10.7分钟，从第 - 14天到第 - 1天，间隔为44.0±5.3分钟（P<0.05）。从第 - 60天到第 - 25天，OT峰值的幅度较低，两条静脉中的情况相似（平均1.37±0.1微单位/毫升）。从第 - 14天到第 - 1天，峰值幅度平均为3.6±0.4微单位/毫升（P<0.02）。在最后2周，子宫卵巢的OT峰值经常高于外周峰值。此外，仅在子宫卵巢静脉中观察到一些峰值（单独峰值）。在分娩第一阶段的当天，峰值幅度增加到7.3±2.0微单位/毫升，峰值间隔比分娩前变短（平均25.1±2.6分钟）。一次大量的OT激增引发了分娩的排出阶段。基础水平分别升至颈静脉的43.1±16微单位/毫升和子宫卵巢静脉的38.7±12.6微单位/毫升，峰值水平分别升至77.4±19.1微单位/毫升和91.6±21微单位/毫升。峰值间隔降至17.2±3.3分钟（P<0.05）。在小牛出生后直到胎盘排出，催产素水平一直很高。在妊娠和分娩的大部分时间里，循环中的OT来源是垂体后叶，但在妊娠后期子宫卵巢静脉中观察到的单独峰值可能起源于黄体或可能起源于肉阜，因为在接近足月时，这两个组织都表达OT mRNA。胎儿垂体后叶是这些峰值的另一个可能来源。我们的结论是，在牛的妊娠期间，OT以低幅度峰值间歇性分泌；接近足月时，峰值的频率和幅度都增加；在分娩期间，血浆OT的急剧增加先于小牛的排出。OT的主要来源是垂体后叶，但接近足月时，子宫卵巢来源会向体循环中分泌额外的OT。
