EFFECTS OF ELEVATED FETAL CORTISOL CONCENTRATIONS ON THE VOLUME, SECRETION, AND REABSORPTION OF LUNG LIQUID

We have examined the role of cortisol in the gestational age-related i ncrease in the ability of epinephrine to inhibit the secretion and ind uce the reabsorption of fetal lung liquid. Chronically catheterized fe tal 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 gestat ion (term similar to 145 days). Lung liquid volumes and secretion rate s were measured at 120 days (before infusion) and at 125 days, and the n at 130 days we tested the ability of epinephrine to inhibit lung liq uid secretion and induce liquid reabsorption. Cortisol infusions incre ased fetal plasma cortisol and 3,5,3'-triiodothyronine (T-3) concentra tions to levels observed just before labor and significantly increased the age-related increase in fetal lung liquid volume and secretion ra te. At 130 days, epinephrine caused a significantly greater rate of lu ng 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, pro bably in conjunction with elevated T-3 concentrations, prematurely inc reases the epinephrine-induced reabsorption of fetal lung liquid. It i s likely, therefore, that the preparturient increase of fetal cortisol concentrations plays an important role in the clearance of lung liqui d at birth.