Wallace M J, Hooper S B, Harding R
Department of Physiology, Monash University, Clayton, Victoria, Australia.
Am J Physiol. 1995 Oct;269(4 Pt 2):R881-7. doi: 10.1152/ajpregu.1995.269.4.R881.
We have examined the role of cortisol in the gestational age-related increase in the ability of epinephrine to inhibit the secretion and induce the reabsorption of fetal lung liquid. Chronically catheterized fetal sheep were infused with either saline (n = 6) or increasing doses of cortisol (1.5-3.5 mg/day; n = 6) between 120 and 130 days of gestation (term approximately 145 days). Lung liquid volumes and secretion rates were measured at 120 days (before infusion) and at 125 days, and then at 130 days we tested the ability of epinephrine to inhibit lung liquid secretion and induce liquid reabsorption. Cortisol infusions increased fetal plasma cortisol and 3,5,3'-triiodothyronine (T3) concentrations to levels observed just before labor and significantly increased the age-related increase in fetal lung liquid volume and secretion rate. At 130 days, epinephrine caused a significantly greater rate of lung liquid reabsorption in cortisol-infused fetuses (10.3 +/- 2.3 ml/h) than in saline-infused fetuses (1.5 +/- 1.6 ml/h). We conclude that a premature elevation in circulating fetal cortisol concentrations, probably in conjunction with elevated T3 concentrations, prematurely increases the epinephrine-induced reabsorption of fetal lung liquid. It is likely, therefore, that the preparturient increase of fetal cortisol concentrations plays an important role in the clearance of lung liquid at birth.
我们研究了皮质醇在与胎龄相关的肾上腺素抑制胎儿肺液分泌及诱导肺液重吸收能力增强过程中的作用。在妊娠120至130天（足月约145天）期间，对长期插管的胎羊分别输注生理盐水（n = 6）或递增剂量的皮质醇（1.5 - 3.5毫克/天；n = 6）。在120天（输注前）、125天测量肺液体积和分泌率，然后在130天测试肾上腺素抑制肺液分泌及诱导肺液重吸收的能力。输注皮质醇使胎儿血浆皮质醇和3,5,3'-三碘甲状腺原氨酸（T3）浓度升高至临产前观察到的水平，并显著增加了与胎龄相关的胎儿肺液体积和分泌率的增加。在130天时，肾上腺素在输注皮质醇的胎羊中引起的肺液重吸收率（10.3±2.3毫升/小时）显著高于输注生理盐水的胎羊（1.5±1.6毫升/小时）。我们得出结论，胎儿循环中皮质醇浓度的过早升高，可能与T3浓度升高共同作用，过早增加了肾上腺素诱导的胎儿肺液重吸收。因此，产前胎儿皮质醇浓度的升高可能在出生时肺液清除中起重要作用。
