The effects of hypophysectomy, thyroidectomy, and postoperative infusion of cortisol or adrenocorticotrophin on the structure of the ovine fetal lung.

We studied the effect of in utero hypophysectomy and replacement therapy with cortisol and adrenocorticotropin on maturation of lung structure in ovine fetuses. Twenty-two festuses underwent hypophysectomy in utero at 99-122 days of fetal gestation. At term (148-150 days), ten fetuses received an infusion of ACTH and six fetuses received an infusion of cortisol. The remaining fetuses were untreated. Morphometric analysis of the caudal lobe of the right fetal lung was performed and included measurement of minimum interalveolar wall thickness, numerical density of Type I and Type II pneumocytes in septal tissue, and volume density of septal tissue and air spaces in respiratory lung. The lung of the hypophysectomized animals differed from term controls in that alveolar walls were thicker, numerical density of Type I pneumocytes was less and that of Type II cells greater. Treatment with ACTH or cortisol caused lung structure to appear similar to the lungs of term control animals. We conclude that hypophysectomy impairs structural maturation and that structural maturation can be achieved by a relatively brief infusion of cortisol or ACTH at term.