Cyclic AMP in macrophages from experimental granulomas and the effect of prostaglandin E2.

Leucocytes were isolated by pronase digestion from granuloma tissue at different stages in inflammation induced by carrageenin-soaked sponge implants in rats and cyclic AMP was measured in these cells. In a mixed cell suspension, containing granulocytes and macrophages, the cyclic AMP levels increased during the early stages of inflammation but decreased when the granuloma became established. However, after correction for the proportion of infiltrating macrophages, as the inflammation progressed only a fall in cyclic AMP content was observable. Exposure of granuloma-derived cells to PGE2 resulted in a rise in cyclic AMP content, which was more pronounced in cells isolated during a later rather than an earlier stage of granuloma development. The results provide support for the earlier proposal that the anti-inflammatory effect of E-type prostaglandins on granulomas is partially explicable on the basis of cyclic AMP changes in infiltrating macrophages.