The role of pulmonary corticosteroid 11-reductase activity in lung maturation in the fetal rat.

Injection of 11-ketoprogesterone into fetal rats at day 17 of gestation reduced the pulmonary C-11 activation index (an indicator of net gain or loss of glucocorticoid activity) as measured at day 21 (P less than 0.001) and resulted in elevated levels of the inactive hormone 11-dehydrocorticosterone (P less than 0.001), but unchanged corticosterone levels. Adrenal weight was significantly increased (P less than 0.001). 11-Ketoprogesterone-injected fetuses had considerably larger lungs (P less than 0.001) with reduced saturated phosphatidylcholine content (P less than 0.001).