Effect of antenatal dexamethasone treatment on Ca2+-dependent nitric oxide synthase activity in rat lung

We investigated the effects of dexamethasone on nitric oxide synthase activity, nitrate/nitrite concentration, and cGMP concentration in the lungs of premature and full-term neonate rats. Dexamethasone or vehicle alone was administered to the mother (1 mg/kg/d, s.c., 2 d), and the neonate was killed 24 h after birth. Ca2+-dependent nitric oxide synthase activity and nitrate/nitrite and cGMP concentrations in lungs of dexamethasone-treated neonates, both premature and full-term, were significantly higher than those in the lungs of the control rats. Ca2+-dependent nitric oxide synthase activity, nitrate/nitrite concentration, and cGMP concentration in the lungs of control rats showed developmentally associated increases during late gestation and in the early postnatal period. The activation of the nitric oxide synthasenitric oxide-cGMP system by antenatal dexamethasone treatment may be related to the improvement of pulmonary function by antenatal glucocorticoid therapy to minimize respiratory distress syndrome.