Effects of beta adrenergic blockade on histamine and prostaglandin-F2 alpha responsiveness in the dog.

To examine whether either the degree of existing beta adrenergic tone or the magnitude of beta adrenergic response during bronchoconstriction might account for the differences that exist between dogs in their pulmonary responsiveness to aerosol challenge with bronchoconstrictor agents, dose-response curves were performed in a group of dogs to either histamine or prostaglandin-F2 alpha, both before beta blockade with propranolol. Beta blocked had no significant effect on control values of dynamic compliance (Cdyn) or resistance of the lung (RL) or on pulmonary responsiveness to prostaglandin f2 alpha. Although propranolol did not have a significant effect on aerosol responsiveness to histamine for the group of dogs taken together, those dogs initially least responsive to aerosol histamine did become more responsive after beta blockade. This effect of beta blockade was statistically significant only for Cdyn and not for RL, suggesting enhancement of peripheral airway effects. We conclude that a beta adrenergic mechanism may contribute to the range of responsiveness found among dogs in their pulmonary responsiveness to histamine but that other as yet undefined factors must also contribute to the differences that exist among dogs in their pulmonary responsiveness to bronchoconstrictor agents.