Progesterone triggers selective mast cell secretion of 5-hydroxytryptamine.

Mast cells are involved in allergic reactions where they secrete numerous mediators in response to immunoglobulin E and antigen. However, they have recently been implicated in neuroinflammatory conditions with a higher prevalence in women, and there have been clinical reports of progesterone anaphylaxis. When tested on purified rat peritoneal mast cells, progesterone alone stimulated release only of 5-hydroxytryptamine (serotonin) in a dose- and time-dependent manner. Serotonin release by progesterone was exceptional because it was not accompanied by histamine release or degranulation and was either augmented or unaffected by drugs which inhibit secretion induced by the classic mast cell secretagogue, compound 48/80. These findings indicate that mast cells are capable of selective serotonin secretion, previously shown only after pretreatment with certain tricyclic drugs, and may be involved in neuroendocrine syndromes.