Walker A M, Oakes G K, Ehrenkranz R, McLaughlin M, Chez R A
J Appl Physiol. 1976 Nov;41(5 Pt. 1):727-33. doi: 10.1152/jappl.1976.41.5.727.
Changes in the uterine and umbilical circulations during induced hypercapnia were studied in nine unanesthetized near-term pregnant sheep. Blood flows were measured with electromagnetic flow transducers and arterial pressures with vascular catheters implanted under anesthesia 2-16 days prior to experiments. Hypercapnia was induced in the fetus alone by giving acetazolamide iv to the fetus, 100-200 mg/kg. Mean fetal arterial Pco2 increased from 49.5 to 63.4 mmHg but no significant changes in umbilical blood flow occurred. Stepwise increases in both maternal and fetal arterial Pco2 were induced by increasing maternal inspired CO2 concentration to a maximum of 12%. No dignificant changes occurred in uterine or umbilical circulations until hypercapnia was severe (maternal arterial Pco2 greater than 60 mmHg, fetal arterial Pco2 greater than 70 mmHg). With severe hypercapnia uterine vascular resistance increased significantly and uterine blood flow decreased despite an increase in maternal arterial pressure; fetal arterial pressure and umbilical blood flow increased significantly, but umbilical vascular resistance did not. We conclude that hypercapnia in conscious pregnant sheep is associated with significant changes in uterine and umbilical circulations, but only when hypercapnia is severe. Carbon dioxide is unlikely to be a factor in normal physiological regulation of the uteroplacental circulation in this species.
在9只未麻醉的近足月妊娠绵羊中研究了诱导性高碳酸血症期间子宫和脐循环的变化。在实验前2 - 16天，于麻醉状态下用电磁血流传感器测量血流量，用血管导管测量动脉压。通过静脉注射乙酰唑胺（100 - 200mg/kg）仅在胎儿中诱导高碳酸血症。胎儿平均动脉血二氧化碳分压从49.5mmHg升至63.4mmHg，但脐血流量未发生显著变化。通过将母体吸入二氧化碳浓度增加至最大12%，使母体和胎儿动脉血二氧化碳分压逐步升高。在高碳酸血症严重（母体动脉血二氧化碳分压大于60mmHg，胎儿动脉血二氧化碳分压大于70mmHg）之前，子宫或脐循环未发生显著变化。严重高碳酸血症时，尽管母体动脉压升高，但子宫血管阻力显著增加，子宫血流量减少；胎儿动脉压和脐血流量显著增加，但脐血管阻力未增加。我们得出结论，清醒妊娠绵羊中的高碳酸血症与子宫和脐循环的显著变化有关，但仅在高碳酸血症严重时。在该物种中，二氧化碳不太可能是子宫胎盘循环正常生理调节的一个因素。
