EFFECT OF CORTISOL ON THE MATURATION OF FETAL RABBIT LUNGS

Abstract

The effect of cortisol on the maturation of fetal lungs was investigated in two series of experiments in rabbits. In one series cortisol (10 to 30 mg/kg) was injected into 16 pregnant does for 3 days. Twenty-one does were injected with saline and served as controls. In the second series involving 21 does, cortisol (0.5 to 1.0 mg) was injected directly into some fetuses and amniotic sacs 2 to 3 days prior to premature delivery while their littermates were given saline and were used as controls. Fetuses were delivered by cesarean section at gestational ages between 26 and 29 days (full term: 30 days). Following maternal injection many fetuses were dead at delivery and the remaining live fetuses were smaller and weighed less than controls. There was no evidence of accelerated lung maturation. Fetuses directly injected with cortisol were more active, breathed better, and their lungs were better aerated when compared with their control littermates. In treated animals surfactant appeared at 26 to 27 days, a day earlier than controls and on electronmicroscopy there was evidence of accelerated maturation of alveolar epithelial cells. Thus, direct fetal injection of cortisol accelerates maturation of lungs and synthesis of surfactant, and promotes earlier extra-uterine adaptation of premature fetuses.