Alpha- and beta-adrenergically mediated responses in isolated lung strips of guinea pigs.

Thin strips of lung parenchyma from guinea pigs were mounted in an isolated tissue bath and placed under an initial tension of 1.2 gm. Drug-induced changes in resting tension were recorded isometrically upon the addition of representative alpha- and beta-adrenergic agonists. Lung strips relaxed following challenge with isoproterenol, 10(-9) to 10(-6)M (beta-adrenergic agonist), and contracted following challenge with phenylephrine, 10(-6) to 10(-4)M (alpha-adrenergic agonist). The responses of lung strips to norepinephrine, 10(-8) to 10(-4)M (mixed alpha- or beta-agonist) were influenced by the presence of either an alpha- or beta-adrenergic antagonist: pretreatment with phentolamine, 10(-5)M (alpha-antagonist) resulted in relaxant responses to norepinephrine, whereas pretreatment with propranolol, 10(-5)M (beta-antagonist) resulted in contractile responses. Cocaine, an uptake-1 inhibitor, potentiated the contractile effect of norepinephrine but not the relaxant effect of isoproterenol or norepinephrine. These data support the existence of alpha- and beta-adrenergic receptors mediating contraction and relaxation, respectively, in guinea pig lungs.