Synergistic action of triiodothyronine and hydrocortisone on epinephrine-induced reabsorption of fetal lung liquid.

The influence of triiodothyronine and hydrocortisone on maturation of the response to epinephrine that leads to reabsorption of lung liquid was investigated in nine chronically catheterized fetal sheep. Experiments were performed on thyroidectomized fetal sheep at 116-120 d gestation, well before the reabsorptive response to epinephrine is normally seen. After i.v. administration of either triiodothyronine (60 micrograms/d) or hydrocortisone (10 mg/d) for 3 d (three fetuses in each case), all fetuses continued to secrete lung liquid during exposure to epinephrine (secretion rate = 5.9 +/- 3.2 mL/h in triiodothyronine-treated and 4.4 +/- 1.9 mL/h in hydrocortisone-treated fetuses). However, when the two hormones were administered together in the same doses to three fetuses, a striking reabsorptive response to epinephrine was seen (absorption rate = -12.3 +/- 3.6 mL/h), similar to that observed in the mature fetus. Induction of this capacity to reabsorb lung liquid may be of importance in the management of respiratory problems of the newborn infant.