Histamine-potentiating activity in rat anaphylactic pleural fluid: role of serotonin

The identity of the histamine-potentiating activity detected in the rat anaphylactic pleural washing was investigated. Wistar rats of both sexes, weighing 150-200 g, were sensitized by injecting subcutaneously (sc) a mixture of ovalbumin and Al(OH)3 14 days before allergen challenge. In sensitized rats, intrapleural (ipl) injection of ovalbumin (l2 mug/cavity) caused an intense protein exudation. A single ipl administration of compound 48/80 (l2 mug/cavity) exhausted the resident mast cell population and turned the pleural cavity hyporeactive to the allergen challenge performed 5 days later. Allergen-induced exudation occurred in parallel to a dramatic decrease in the amount of cell-stored histamine (from 9.6 n 1.4 (N = 8) to 1.3 n 0.1 (N = 6) mug/cavity, P