Three day pleural inflammation: a new model to detect drug effects on macrophage accumulation.

Mononuclear cell accumulation is of major importance in maintaining chronic inflammatory conditions. In an effort to model this phenomenon, 0.3 ml of a 1% carrageenan solution was injected into the pleural cavity of rats; at various times thereafter peripheral blood and pleural exudate samples were collected. Seventy-two hours after carrageenan injection, 82.3 +/- 3.7 x 10(6) cells (N = 6; mean +/- S.E.) were present in the pleural cavity; over 80% of these cells were macrophages as determined by morphologic and histochemical criteria. Animals treated with dexamethasone had a significantly reduced number of pleural macrophages. Animals treated with the nonsteroidal anti-inflammatory agents, naproxen and indomethacin, had an elevated intrapleural macrophage content. The number of intrapleural cells was not affected by the antirheumatic agents levamisole, d- and dl-penicillamine or gold sodium thiomalate. Animals treated with tilorone, dapsone, hydroxychloroquine, phenylmethane-sulfonyl fluoride and 1,10 phenanthroline had a reduced pleural cell count.