DEXAMETHASONE INCREASES BETA(2)-ADRENOCEPTOR-REGULATED PHOSPHATIDYLCHOLINE SECRETION IN RAT ALVEOLAR TYPE-II CELLS

Insufficient production of pulmonary surfactant in alveolar type II ce lls is relevant to many lung diseases. To cure its deficiency, glucoco rticoid is commonly used in clinical areas. In the present study, we i nvestigated the effect of dexamethasone on the secretion of phosphatid ylcholine, a major phospholipid of pulmonary surfactant, in a primary culture of rat alveolar type II cells. Dexamethasone had no effect on the basal secretion rate of phosphatidylcholine. Dexamethasone augment ed both the phosphatidylcholine secretion and the cyclic AMP formation increased by terbutaline. Furthermore, dexamethasone increased the nu mber of beta-adrenoceptors and mRNA expression of beta(2)-adrenoceptor s in type II cells. These findings indicate that dexamethasone increas es pulmonary surfactant secretion through an enhancement of beta(2)-ad renoceptor gene expression.