Cortisol metabolism by the lung.

James I. %Vessel, B.S.; and Brandon Taylor, B.S. G lucocorticoids have been recognized to play an important role in lung development in utero.’ The identification of specific receptors for cortisol in both the cytosol and nuclear fraction of fetal lung homogenates supports the concept that the lung is an important target tissue for this steroid.2.3 Administration of cortisol to rabbit fetuses at appropriate stages of gestation accelerates morphologic development of lungs and causes precocious appearance of pulmonary surfactant. ’ In fetal rabbit lungs, the specific cortisol cytosol receptors reach a maximum concentration at 28-30 days, just prior to term, when surfactant can be identified in alveolar washings.6 The concentration of these specific cortisol binding sites in nuclear fractions have been shown to be greater in lung than in liver. While cortisol is the predominant active glucocorticoid in human plasma, cortisone, its 1 1-keto oxidized metabolite is much less active. It undergoes reduction to cortisol by the enzyme 11-beta dehydrogenase for development of steroid activity. It has been reported that the blood of human newborns contains 2-5 times more cortisone and %-‘ less cortisol than maternal blood.79 In fact, the ratio of cortisone to cortisol in the blood may be up to 18 times greater in newborns than in mothers. These studies suggest that cortisone may also play a role in human lung maturation. The present investigation was designed to study cortisol metabolism in adult and fetal rabbit lungs.