MATURATION OF THE FETAL LUNG

Publisher Summary This chapter discusses a study to analyze maturation of the fetal lung. Lung maturation was studied in hypophysectomised (Hx) fetal lambs, some of which were thyroidectomised (Tx) in addition to exclude effects of prolactin and thyroid hormones. Lung maturation was assessed by histological examination and pressure–volume curves. Fetal hypophysectomy was performed cryosurgically at 99–122 days (term 150 days) and completeness assessed by measuring the response of plasma prolactin to a 100 μg bolus of TRF and by the histological examination of the pituitary fossa. These studies confirm the importance of the fetal adrenal in lung maturation in fetal sheep but suggest in addition that heightened activity of the adrenal medulla as well as the cortex is necessary. Lung maturation occurs in the presence of very low levels of thyroxine and triiodothyronine (after Hx) but is impaired in their absence (after Hx + Tx), suggesting that thyroid hormones hormones have a premissive function. These observations are in agreement with conclusions drawn from fetal infusions of prolactin that this hormone is not essential for lung maturation.