REGULATION OF LUNG LIQUID SECRETION IN IMMATURE FETAL SHEEP - HORMONAL INTERACTION

The present studies were designed to test the hypothesis that arginine vasopressin (AVP) can interact with hydrocortisone and 3,5,3'-triiodothyronine (T-3) to induce maturation of lung liquid reabsorptive processes in fetal sheep <130 days gestation. Lung liquid production rates were measured in chronically catheterized thyroidectomized fetal sheep during eight different experimental treatments. Each experiment consisted of a 2-h control period followed by a 5-h treatment period. Net secretion or reabsorption of lung liquid was measured by using impermeant marker dilution techniques. AVP alone (50 mU/kg bolus plus 5.0 mU . kg(-1) . min(-1) iv infusion) does not alter lung liquid secretion in fetal sheep 125 +/- 0.72 (SE) days gestation. In contrast, AVP (same dose as above) with T-3 (30 mu g) and hydrocortisone (8.94 mg/min) depressed lung liquid secretion and caused reabsorption of fluid. T-3 alone, T-3 and hydrocortisone, T-3 and AVP, hydrocortisone alone, hydrocortisone and AVP, and saline did not result in net lung liquid reabsorption over a 5-h treatment period. These investigations demonstrate that AVP, T-3, and hydrocortisone interact to cause lung liquid reabsorption in immature fetal lungs.