The effect of serotonin (5-hydroxytryptamine) and derivatives on guanosine 3',5'-monophosphate in human monocytes.

A C T The effects of several putative mediators of inflammatory responses on the cyclic nucleotide con- tent of mononuclear leukocytes from human peripheral blood were investigated. Incubation of mononuclear cells with 100 /AM serotonin (a maximally effective concentra- tion) for 5 min caused a five-to eightfold increase in their content of guanosine 3',5'-monophosphate (cGMP) with no change in adenosine 3',5'-monophosphate (cAMP). Melatonin and related derivatives of 5-hydroxytryptamine, but not tryptamine itself, were as ef- fective as serotonin. Histamine and bradykinin had no effect on cGMP. Polystyrene beads caused accumulation of cAMP in mononuclear cells but did not alter cGMP. On the basis of experiments in which mononuclear cells were divided into adherent (largely monocyte) and non- adherent (largely lymphocyte) populations, it was con- cluded that the monocytes accumulate cGMP in response to serotonin. It is suggested that serotonin and cGMP may play a role in monocyte motility or migration.