Stimulation of histamine synthesis from tumour cells by concanavalin A and A23187

In the present study the amount of histamine synthesized by two experimental tumour cell lines, the Yoshida ascites sarcoma cells and SEWA cells, was measured after stimulation in vitro with the calcium ionophore A23187 and the plant lectin Concanavalin A (Con A). After 7 hrs of incubation with the two stimulators, histamine could be measured and the amount was still increasing up to 15 hrs of incubation with a maximal net histamine production of approximately 1.0 ng histamine per 10(6) tumour cells per ml sample. In addition, the tumour promoter 12-O-tetradecanoyl-phorbol-13-acetate (TPA) was found to enhance the synthesis of histamine in the presence of Con A or A23187, except in high concentrations, i.e. 50 ng/ml TPA, where an inhibitory effect was seen. TPA alone could not induce detectable histamine synthesis. In order to measure the histamine, the tumour cells were incubated in glass microfibre-based microtiter plates, which have been shown to bind histamine with high affinity and selectivity. The aim has been to develop a functional in vitro tumour assay which can detect histamine from tumour cells and which can be used to measure pharmacological interaction of the tumour cell function as well as histamine production from different tumour cell types.