Differential effect of dexamethasone and hydrocortisone on alveolar growth in rat pups.

Glucocorticoids are widely used in perinatology, since they decrease the incidence of respiratory distress syndrome and chronic lung disease. However, evidence is now increasing that their use in this age group may result in impaired alveolar lung growth and general development. The aim of this study was to determine whether a low dose of hydrocortisone (1 mg/kg/day for 11 days) was deleterious to lung growth in rat pups, as compared to an equivalent dose of dexamethasone.

Pharmacologically induced relaxation of tracheal smooth muscle is increased in hyperoxia-exposed 15-day-old rats.

Hyperoxia increases maximum airway contractility in newborn guinea pigs and immature rats. Studies examining the mechanisms of hyperoxia-induced airway hyperresponsiveness have focused on contractile mechanisms, although excessive airway narrowing could be due to impaired relaxation. Our objective was to determine the effects of hyperoxia on airway structure and relaxing properties in juvenile rats exposed to an inspired fraction of oxygen (FiO(2)) of 0.