Transplacental clearance and blood flows of bovine gravid uterus at several stages of gestation.
Transplacental clearance and blood flows of bovine gravid uterus at several stages of gestation.
复制标题
牛妊娠子宫在妊娠几个阶段的经胎盘清除率和血流。
DOI：
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发表时间：
1987
影响因子：
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通讯作者：
C. Ferrell
中科院分区：
文献类型：
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作者：
L. Reynolds;C. Ferrell
测定奶牛在妊娠137 +/- 1.0 （SE, n = 9）、180 +/- 0.5 （n = 8）、226 +/- 0.4 （n = 9）和250 +/- 1.8 (n = 5) d时子宫和脐血流量及经胎盘氧化氘（D2O）清除率。从第137天到第250天，子宫血流量增加4.5倍，脐血流量增加21倍，D2O清除率增加14倍。脐血流量和D2O清除率的变化与胎儿生长和代谢速率的增加是平行的，这在以前的报道中发生在妊娠的后半期。D2O清除率对子宫和脐血流量的回归有显著性意义（P < 0.01），可解释胎盘D2O清除率变化的94-99%。由于D2O的清除率总是低于子宫和脐带血流的清除率，并且由于一个相对简单的统计模型解释了清除率的大部分变化，因此表明母体和胎儿胎盘微血管的并发或逆流排列不足以解释高弥散性物质穿过牛胎盘的清除率。此外，数据的胎盘交换图显示存在母体和胎儿胎盘血流严重不均匀分布和/或母体和胎儿胎盘血流明显分流离开交换区域。综上所述，这些数据表明，奶牛的胎盘，就像绵羊和山羊的胎盘一样，代表了一个相对低效的胎盘交换系统。
Rates of uterine and umbilical blood flows and transplacental clearance of deuterium oxide (D2O) were determined for cows on 137 +/- 1.0 (SE, n = 9), 180 +/- 0.5 (n = 8), 226 +/- 0.4 (n = 9), and 250 +/- 1.8 (n = 5) days of gestation. From days 137 to 250, rates increased 4.5-fold for uterine blood flow, 21-fold for umbilical blood flow, and 14-fold for clearance of D2O. Changes in rates of umbilical blood flow and D2O clearance paralleled increased rates of fetal growth and metabolism, which have previously been reported to occur during the last half of gestation. The regressions of D2O clearance on uterine and umbilical blood flows were significant (P less than 0.01) and explained 94-99% of the variation in placental clearance of D2O. Because the rate of D2O clearance was always less than that of uterine and umbilical blood flows, and because a relatively simple statistical model explained most of the variation in clearance, it was suggested that a concurrent or countercurrent arrangement of maternal and fetal placental microvasculatures is not adequate to explain clearance of highly diffusable substances across the bovine placenta. In addition, a placental exchange diagram of the data showed the existence of severe uneven distribution of maternal and fetal placental blood flows and/or significant shunting of maternal and fetal placental flows away from areas of exchange. Taken together, these data indicate that the placenta of the cow, like those of the sheep and goat, represents a relatively inefficient system of transplacental exchange.