Participation of the Adrenal in the Lung Development during Fetal Life in Rats

Abstract

The main purpose of this study was to examine the relationship between the lung alveolar development and the fetal adrenal activity, by means of fetal bilateral adrenalectomy. The bubble stability ratio (BSR), to detect the changes in the amount of pulmonary surfactant, was determined in the lungs of rat fetuses and neonates or fetuses retained in utero beyond the normal gestation period. Histologic examination of lung alveolar tissue was also performed. The BSR in normal rats was gradually increased toward term and was still high at 2hr after birth, followed by a subsequent decline in the 1st and the 2nd day after birth. This change was in parallel with the histologic observation that the alveolar walls became progressively thinner whereas the number of great alveolar cells showed a prenatal increase followed by a postnatal decrease. Prolongation of gestation, induced by a maternal injection of progesterone, maintained the late fetal state in the BSR and the lung histology. Fetal adrenalectomy caused a decline in the BSR and a retardation in histologic differentiation of the fetal lung alveolar tissue. These effects were overcome by giving corticosterone to the adrenalectomized fetuses. The results support the view that the fetal adrenal gland participates in the development of great alveolar cells and the surfactant production before birth.