Inflammatory pleuropulmonary fibrosis in essential fatty acid deficient rats and the lack of response to methysergide.

In view of the association between essential fatty acid (EFA) deficiency and human cystic fibrosis, we have investigated the possible occurrence of pulmonary disease in rats fed an EFA deficient (EFAD) diet for 40 weeks. In contrast to a few slight spontaneous lesions consisting of pleural membrane hyperplasia, which were found in the lungs of control rats, a much greater incidence of fibrotic lesions was observed in the lungs of EFAD rats. These pleuropulmonary fibroses extended from the hyperplastic pleural membrane into the alveoli and were characterized by collagen deposition and marked macrophage infiltration to the extent that, in some cases, the alveolar septa were completely obstructed by inflammatory exudate. These findings lend indirect support to the contention that EFA deficiency plays a role in the aetiology of cystic fibrosis, at least with regard to pulmonary lesions. Administration of methysergide (10 mg/kg/day, p.o.) for a total of 11 weeks, did not alter the incidence of fibrosis in the lungs of EFAD rats, despite the finding that a man who had developed pleuropulmonary fibrosis as a result of chronic methysergide treatment exhibited a relative serum EFA deficiency. While a relative EFA deficiency may be a predisposing factor for the induction of fibrosis by chronic methysergide treatment, our data are not sufficient to make a decision upon this hypothesis.