Cyclic 3',5' adenosine monophosphate (cAMP) is a second messenger of the beta adrenergic receptor (betaAR). Ketamine causes an increase in the intracellular accumulation of cAMP in several non-human tissue preparations. A "species effect" may explain the differing results of ketamine on betaAR mediated responses, thus reports of a ketamine-induced increase in cAMP in other species may not be applicable to humans. The effect of ketamine (10(-3), 10(-4), or 10(-5) M) pretreatment (60 and 120 min) on isoproterenol ISO, a beta adrenergic receptor (AR) agonist or forskolin FSK, an activator of adenylylcyclase (AC)-induced intracellular accumulation of cAMP in a human airway smooth muscle (tracheal) cell line (HASM) was evaluated. In an in vitro HASM culture, cells with or without pretreatment were labeled with 3Hadenine to produce 3HATP, and following stimulation with ISO or FSK to convert the 3HATP to 3HcAMP, the intracellular accumulation of 3HcAMP was measured by sequential chromatography over Dowex and alumina columns. Pretreatment of the HASM cells with ketamine (10(-3) and 10(-4) M) caused a reduction (P < 0.05, when compared to untreated cells) in ISO-induced cAMP accumulation, but did not effect cAMP accumulation following FSK stimulation. This effect of ketamine was greater at 120 min of pretreatment than at 60 min (10(-3) M ketamine only)(P < 0.05). No effect was found at either time period following pretreatment of the HASM cells with ketamine 10(-5) M. These results demonstrate that pretreatment of the HASM cells with ketamine reduces ISO-induced cAMP accumulation. Since only ISO-induced cAMP was effected by ketamine, these data suggest that ketamine inhibits production of cAMP proximal to AC in the cAMP production pathway. These results also demonstrate that a mechanism other than that involving the betaAR and intracellular cAMP accumulation is responsible for the ketamine induced bronchodilation in humans.