[Interactions between angiotensin II and theophylline on isolated rat bronchi]

For more than half of century physicians are using theophylline for the treatment of obstructive pulmonary diseases. Because our previously results suggested the amplification of intrapulmonary renin angiotensin system (RAS) on ovalbumin (OVA) induced airway hyperresponsiveness we studied the interaction between theophylline and angiotensin II (Ang II) on normal versus sensitized rats.

we used main left bronchial rings mounted in wire myograph to assess the effects of Ang II and theophylline on airway smooth muscle.

On both normal and OVA sensitized rats theophylline did not significantly modify either Ang II contractile effects or Ang II amplification of acetylcholine (ACh)-induced bronchoconstriction. On the other hand, on sensitized rat after antigen challenge, theophylline pretreatment reduced Ang II inhibition of terbutaline--induced relaxation of bronchial rings precontracted with ACh, increasing both EC50 and E(max) of terbutaline effects with 22.04 +/- 3.48% and 19.48 +/- 1.67%, respectively.

These findings suggested that, in addition to bronchodilatory and antiinflammatory actions, theophylline could block some effects of intrapulmonary RAS activated in pathologically states as antigen sensitization and challenge.