Carrageenan-induced pulmonary emphysema of rabbit.

Abstract

A transbronchial injection of 0.75% carrageenan in physiologic saline induced pneumonia followed by emphysema in the insulted lobe. In the stages of pneumonia, scattered infiltration of polymorphonuclear leukocytes was seen throughout the affected lobe within a few days of treatment; later this was replaced by the accumulation of carrageenan-laden macrophages, which lasted for one to two months. Enlargement of alveoli and alveolar ducts appeared 2 weeks to 2 months after the treatment, and pulmonary emphysema was observed at 4 months. The lobes that were not treated with carrageenan were normal in appearance during both the pneumonia and the emphysema. Morphometric analysis of the lung at 4 months showed decrease of the alveoli and/or alveolar ducts and enlargement of their luminal spaces, also suggesting the development of emphysema. In contrast to various kinds of elastases that are known to produce emphysematous changes in animals, the elastolytic activity of carrageenan solution did not show any such effects, although in the homogenate of the lobes given carrageenan, a moderate but significant increase in the proteinase activities of alveolar macrophages are said to occur (Bowers et al. 1985). It was suggested that carrageenan-induced emphysema is a chronic disorder associated with both carrageenan toxicity and accumulated carrageenan-laden macrophages in the insulted lobes.