EXPERIMENTAL RADIATION PNEUMONITIS .4. LEAKAGE OF CIRCULATORY PROTEINS ONTO THE ALVEOLAR SURFACE

  • 1 January 1980
    • journal article
    • research article
    • Vol. 95  (1) , 19-31
Abstract
The fall in lung compliance in radiation pneumonitis is mainly due to abnormality of the alveolar surface lining layer. This abnormality is possibly due to an increased amount of protein in the alveolar lining fluid layer. This extra protein was partially characterized, and the kinetics of permeation from the blood to the lung and AF [Alveolar fluid] were investigated using i.v. injected 125I-labeled albumin. Mice receiving 3000 rad to the thorax were used. A 4-5-fold increase in the total protein in AF obtained by pulmonary lavage was again found in mice irradiated 4 mo. previously, as compared to control littermates. With immunologic techniques and polyacrylamide disc-gel electrophoresis the excess protein in the alveolar lavage fluid was found to derive from the circulation. Following injection of 125I-labeled albumin into the tail vein, APR [acid-precipitable activity] in the perfused, lavaged lung relative to radioactivity in blood, rose to a plateau at 6 h which was approximately twice as high in irradiated mice as in controls. APR in the AF rose rapidly relative to the blood and continued to rise throughout the period of study, reaching a level 6 times the control mice in 24 h. A major abnormality in radiation pneumonitis appears to be a large increase in permeability of the capillary and alveolar membranes to small and large protein molecules. These abnormalities are not acute terminal events but probably persist for some wk before death. Leakage of plasma proteins onto the alveolar surface is apparently responsible for the fall in compliance of the AF lining layer in radiation pneumonitis.