Isolated lung strips of guinea pigs: responses to beta-adrenergic agonists and antagonists.

Isolated lung strips of guinea pigs were examined as an in vitro model for assessing the direct effect of beta-adrenergic drugs at the level of peripheral airways. Changes in intrinsic tone of thin strips of lung parenchyma were measured with an isometric force transducer. Isoproterenol, a nonselective beta-adrenergic agonist, and several beta-adrenergic agonists, soterenol, salbutamol, metaproterenol and ritodrine elicited a dose-related relaxation of lung strip. Responses to isoproterenol were antagonized by propranolol and the selective beta blocking agents butoxamine (beta2) and practolol (beta1). These results were compared to data obtained with the same compounds on isolated guinea pig atria. All agonists except ritodrine were full agonists in the lung strip whereas isoproterenol and metaproterenol were the only full agonists in the atrial preparation. In the atria, practolol was a more effective blocker of isoproterenol responses than butoxamine, and the reverse was true for the lung strip.