The perfused guinea-pig lung revisited: A study of EDRF-NO system

Adult male guinea pigs from both sexes were anaesthetized with pentobarbita l (40mg/Kg). After tracheotomy the lungs were perfused with Krebs-Henseleit solution at 37 degrees C in a non recirculated system composed of a perfus ion pump, a transducer to measure pressure and another one to measure bronc hial resistance. In all groups studied histamine injections were made at th e doses of 50, 100, 200 and 400 mug/ml as a bolus. Propranolol (1 mug/ml) a dded 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 mug/ml) was added to the perfusate, a great increase i n histamine induced bronchoconstriction was observed, that was followed by a remarkable increase in perfusion pressure, Methylene blue at the dose of 8.25 mug/ml increased bronchorreativity as well as the perfusion pressure s ignificantly. L-arginine (3.5 mug/ml) added to the perfusate, did not promo te reactivity. The addition of L-arginine plus NADPH (1 mug/ml), promoted a significant decrease in bronchoconstriction (p<0.01). In both cases, perfu sion pressure increased when compared to controls. Nitroarginine (2.5<mu>g/ ml) greatly increased perfusion pressure with no change in broncho constric tion. Therefore, we conclude that nitric oxide (NO) is a very important mod ulator for keeping the low perfusion pressure and bronchodilation of the is olated perfused guinea pig lung.