Cyclic AMP and allergic histamine release. Influence of methylxanthines on rat mast cells.

Both isobutylmethylxanthine and theophylline increased the level of cyclic AMP in rat mast cells. Theophylline reduced the allergic histamine release, whereas isobutylmethylxanthine caused a pronounced potentiation of the histamine release. This indicates that the hypothesis of an inverse relationship between the level of cyclic AMP in mast cells and histamine release is inadequate.