The perfused guinea-pig lung revisited: a study of EDRF-no system

Adult male guinea pigs from both sexes were anaesthetized with pentobarbital (40mg/Kg). After tracheotomy the lungs were perfused with Krebs-Henseleit solution at 37 degrees C in a non recirculated system composed of a perfusion pump, a transducer to measure pressure and another one to measure bronchial resistance. In all groups studied histamine injections were made at the doses of 50, 100, 200 and 400 microg/ml as a bolus. Propranolol (1 microg/ml) added to the perfusate, promoted a remarkable increase in perfusion pressure (p<0.001) and a significant augmentation in bronchoconstriction (p<0.05). When indometacin (10 microg/ml) was added to the perfusate, a great increase in histamine induced bronchoconstriction was observed, that was followed by a remarkable increase in perfusion pressure. Methylene blue at the dose of 8.25 microg/ml increased bronchorreativity as well as the perfusion pressure significantly. L-arginine (3.5 microg/ml) added to the perfusate, did not promote reactivity. The addition of L-arginine plus NADPH (1 microg/ml), promoted a significant decrease in bronchoconstriction (p<0.01). In both cases, perfusion pressure increased when compared to controls. Nitroarginine (2.5 microg/ml) greatly increased perfusion pressure with no change in bronchoconstriction. Therefore, we conclude that nitric oxide (NO) is a very important modulator for keeping the low perfusion pressure and bronchodilation of the isolated perfused guinea pig lung.