The effect of cortisone on established silicotic fibrosis in the lungs of rats.

In man, cortisone has not been shown to have any appreciable effect on long-standing fibrosis. Kennedy, Pare, Pump, Beck, Johnson, Epstein, Venning, and Browne (1951) treated a case of pulmonary silicosis with some clinical improvement in the patient's condition, although this was not supported by the x-ray findings; and Kennedy (1954) has recently reported rather similar findings (subjective but no objective improvement) in pneumoconiotic potters and coal-miners. Harrison, King, Dale, and Sichel (1952) investigated the action of cortisone on developing fibrous tissue in the lungs of rats produced by intratracheal injection of quartz particles. Cortisone appeared to interfere with the migration of dust-laden phagocytes in the lung, where they remained diffusely distributed within alveoli instead of aggregating to form discrete nodules. It also modified the development of pulmonary silicotic nodules in amount and distribution, but did not significantly alter the maturation of fibrous tissue from reticulin to collagen. Marenghi and Rota (1954), however, concluded from their experiments with cortisone treatment of quartz-dusted rats that cortisone had very little influence on the initial cellular reaction, but that it delayed or prevented the transformation of reticulin into collagen in the later stages of the fibrotic process. Curran (1952) showed that cortisone had no effect on existing silicotic lesions in the peritoneum of mice. Magarey and Gough (1952), working with rabbits, were unable to find any reduction of mature fibrous tissue in intraperitoneal silicotic nodules as a result of cortisone treatment, although histological evidence suggested that the administration of cortisone retarded the further proliferation of fibroblasts with consequent retardation of concentric fibrosis in the nodules, preformed collagen remaining unaltered. It is concluded that cortisone has a modifying effect on developing silicotic fibrosis in the peritoneum and lungs of experimental animals, while its action on established silicotic fibrosis is less definite. It seemed desirable, therefore, to study the effect of cortisone on established silicotic fibrosis in the lungs of rats, with particular reference to the histological picture as well as to the collagen and silica content of the lungs.