Shinozuka N, Yen A, Nathanielsz P W
Laboratory for Pregnancy and Newborn Research, Department of Biomedical Sciences, College of Veterinary Medicine, Cornell University, Ithaca, New York 14853-6401, USA.
Am J Physiol Heart Circ Physiol. 2000 Jan;278(1):H41-9. doi: 10.1152/ajpheart.2000.278.1.H41.
Fetal cardiovascular responses to an altered intrauterine environment of increased myometrial contractures induced by oxytocin (OT) pulses to the ewe over the final 50 days of gestation were studied in chronically instrumented sheep. Ewes received saline (Cntl) or long-term OT treatment (LTOT, 600 microU x kg(-1) x min(-1) in 5-min pulses every 20 min) from 96 days gestational age. Fetal baroreflex responses to sodium nitroprusside (SNP) and phenylephrine (PE) were studied at 133 days gestation. OT increased contractures in LTOT ewes. Fetal blood pressure (FBP) was higher, and fetal heart rate (FHR) and slope of daily change in FBP and FHR were lower in LTOT fetuses. Fetal SNP-induced hypotension resulted in a narrow R-R interval variation range in LTOT fetuses; Cntl fetuses showed early breakdown in compensation. Baroreflex response slope during PE-induced fetal hypertension was lower in LTOT than in Cntl fetuses. Although the cortisol-to-ACTH ratio was lower in LTOT fetuses, fetal plasma ACTH and cortisol changes were similar in control and LTOT fetuses. We hypothesize that contracture-induced alterations in the intrauterine environment accelerate fetal cardiovascular development through mild hypoxemia, repetitive fetal pituitary-adrenal stimulation, and/or physical stimulation.
在慢性植入仪器的绵羊中，研究了在妊娠最后50天内，催产素（OT）脉冲诱导母羊子宫肌层挛缩增加导致子宫内环境改变时胎儿的心血管反应。从妊娠96天起，母羊接受生理盐水（Cntl）或长期OT治疗（LTOT，600微单位×千克⁻¹×分钟⁻¹，每20分钟进行5分钟脉冲注射）。在妊娠133天时，研究了胎儿对硝普钠（SNP）和去氧肾上腺素（PE）的压力反射反应。OT增加了LTOT母羊的子宫肌层挛缩。LTOT胎儿的胎儿血压（FBP）较高，而胎儿心率（FHR）以及FBP和FHR的每日变化斜率较低。胎儿SNP诱导的低血压导致LTOT胎儿的R-R间期变化范围变窄；Cntl胎儿在代偿方面出现早期崩溃。LTOT胎儿在PE诱导的胎儿高血压期间的压力反射反应斜率低于Cntl胎儿。尽管LTOT胎儿的皮质醇与促肾上腺皮质激素（ACTH）比值较低，但对照胎儿和LTOT胎儿的胎儿血浆ACTH和皮质醇变化相似。我们推测，挛缩引起的子宫内环境改变通过轻度低氧血症、反复的胎儿垂体-肾上腺刺激和/或物理刺激加速了胎儿心血管发育。
