Effect of three weeks' treatment with budesonide on in vitro contractile and relaxant airway effects in the rat.

An investigation was carried out to determine whether the sensitivity of rat tracheal smooth muscle to contractile and relaxant drugs was affected by three weeks' treatment with subcutaneous budesonide before death. Budesonide treatment was associated with a lower thymus weight and a smaller gain in body weight than in control animals. There was, however, no difference in the carbachol concentration-response curves or maximum responses to carbachol of tracheal smooth muscle from control and budesonide treated rats. Isometric and isotonic recordings agreed in these respects. Glucocorticoid treatment did not increase the sensitivity of tracheal smooth muscle to the relaxant drugs terbutaline and enprofylline; if anything there was a tendency for terbutaline and enprofylline to be less potent after budesonide treatment. The data suggest that in vivo effects of glucocorticoids on airway responsiveness to bronchodilating and bronchoconstricting drugs are unlikely to be due to a direct effect on bronchial smooth muscle.