Croton oil pleurisy induces pulmonary hyperreactivity.

Inflammatory process of the airways has been claimed to be relevant to the development of bronchial hyperreactivity in different experimental models. We investigated the consequences of pleural inflammation induced in the guinea-pigs by croton oil injection into the pleural space. Croton oil injection was followed by the development of an inflammatory reaction localized to the pleura as shown by recovery of inflammatory exudate from the pleural cavity of treated animals. An increased number of white cells was observed in the pleural fluid of treated animals as compared to control. Moreover, the croton oil induced inflammation was characterized by development of pulmonary hyperreactivity which involved both airway and vascular smooth muscles. We also studied this phenomenon in an animal model of asthma, such as the actively sensitized guinea-pigs. Polymorphonuclear leukocyte and particularly eosinophil recruitment was increased in this experimental condition and a different trend in the development of the hyperreactive phenomenon was observed. Our data support the relationship between inflammatory process within the pleural space and increased reactivity of pulmonary tissues. The possible involvement of different classes of white cells in this phenomenon has also been discussed.