Surfactant function affected by airway inflammation and cooling: possible impact on exercise-induced asthma

Pulmonary surfactant maintains patency of narrow conducting airways, An inf lammation, with a leakage of plasma proteins into the airway lumen, causes surfactant to lose some of this ability. Will a lowering of temperature agg ravate the deteriorating effect of an inflammation? Calf lung surfactant extract (CLSE) with proteins added was studied with a capillary surfactometer (CS) at temperatures of 25-42 degrees C. BALB/c mic e were infected with respiratory syncytial virus (RSV). Six days later the lungs were lavaged and the surfactant in the lavage fluid was studied with the CS at temperatures of 25-42 degrees C. Lavage fluid from allergen chall enged asthmatics was examined for its content of surfactant inhibitors at r educed temperatures. It was shown that CLSE with proteins gradually lost its ability to maintain patency as the temperature was lowered. Lavage fluid from the RSV infected mice showed a similar dysfunction at Low temperatures. Lavage fluid from t he airways of human asthmatics, when challenged with antigen but not with s aline, contained agents inhibiting surface activity, particularly at reduce d temperatures. Airway inflammation causes surfactant to lose its ability to maintain paten cy, particularly as the temperature is reduced. That might be a reason for the increased airway resistance observed in asthma patients hyperventilatin g in cold weather.