Effect of propranolol on pulmonary function and bronchoconstrictor responsiveness in guinea pigs and rats.

The beta-blocker propranolol was studied for its effects on basal pulmonary functions and on bronchoconstrictor responses to methacholine and histamine in mechanically ventilated guinea pigs and rats. Using doses that blocked the antibronchoconstrictor (bronchodilator) effects of the beta 2-agonist salbutamol, propranolol had no measurable effect on basal airway resistance and dynamic lung compliance in both guinea pigs and rats. However, bronchoconstrictor responses to methacholine and histamine were augmented by propranolol in guinea pigs. In contrast, propranolol did not change bronchoconstrictor responses to methacholine in rats. These results are discussed in terms of the functional role of pulmonary beta-receptors in guinea pigs and rats.