Alvaro R, de Almeida V, al-Alaiyan S, Robertson M, Nowaczyk B, Cates D, Rigatto H
Department of Pediatrics, University of Manitoba, Winnipeg, Canada.
J Dev Physiol. 1993 Jan;19(1):23-8.
Umbilical cord occlusion in the presence of adequate oxygenation induces continuous breathing and arousal in the chronic unanesthetized fetal sheep preparation. The mechanism responsible for this is unknown. We hypothesized that if a placental factor is responsible for the inhibition of breathing in the fetus, the administration of a placental extract while the fetus is breathing continuously after cord occlusion should reverse these changes. Thus, at about 10 min after the induction of continuous breathing by cord occlusion, we administered a placental extract and three subfractions separated by ultrafiltration to 14 chronically instrumented fetal sheep at 133 +/- 1 day gestation. The Krebs solution in which the placental extract was prepared was used as control. Within two minutes of the infusion of the whole placental extract in the carotid artery of the fetus, breathing output (integral of EMGdi x f) diminished in all experiments and was completely abolished in 15/17 (88%). Krebs solution had no effect on breathing. The infusion of subfractions of different molecular weight showed that the inhibition was primarily related to the subfraction between 3.5 and 10 kD. There were no significant changes in blood gas tensions, pH, blood pressure, and heart rate associated with the infusions of the extracts. The ECoG switched from low to high voltage in the majority of the experiments using whole extract and the subfraction 3.5 to 10 kD. These findings suggest that a placental factor, probably a peptide with a molecular weight between 3.5 and 10 kD, inhibits breathing in fetal life.
在充分氧合的情况下，脐带闭塞可使慢性未麻醉的胎羊制剂产生持续呼吸和觉醒。其机制尚不清楚。我们推测，如果胎盘因子是胎儿呼吸抑制的原因，那么在脐带闭塞后胎儿持续呼吸时给予胎盘提取物应能逆转这些变化。因此，在通过脐带闭塞诱导持续呼吸约10分钟后，我们向14只妊娠133±1天、长期植入仪器的胎羊给予胎盘提取物以及通过超滤分离出的三个亚组分。制备胎盘提取物所用的 Krebs 溶液用作对照。在将整个胎盘提取物注入胎儿颈动脉后的两分钟内，所有实验中的呼吸输出（EMGdi×f 的积分）均降低，17例中有15例（88%）完全消失。Krebs 溶液对呼吸无影响。不同分子量亚组分的注入表明，抑制作用主要与分子量在3.5至10 kD之间的亚组分有关。注入提取物后，血气张力、pH、血压和心率均无显著变化。在大多数使用整个提取物和3.5至10 kD亚组分的实验中，脑电图从低电压转变为高电压。这些发现表明，一种胎盘因子，可能是一种分子量在3.5至10 kD之间的肽，在胎儿期抑制呼吸。
