Effect of pH and Temperature on the Uptake of Monoamines by Mouse Peritoneal Mast Cells in Vitro.

The uptake of 5‐hydroxytryptamine, 5‐hydroxytryptophan, noradrenaline and dopamine by normal mouse peritoneal mast cells was studied by means of the histochemical fluorescence method.It was found that 5‐hydroxytryptamine uptake was significantly depressed by increasing pH from 7.0 to 8.9 and by lowering temperature to 20d̀ C when the amine concentration in the incubation medium was 1 μ/ml but not when the concentration was 10 μ/ml.The 5‐hydroxytryptophan uptake was to a high degree affected by similar pH and temperature alterations even when the concentration was as high as 200 μ/ml.This probably reflects a depression of the 5‐hydroxytryptophan decarboxylase activity.Noradrenaline and dopamine uptake was not significantly affected by pH or temperature alterations.These results indicate that normal mouse peritoneal mast cells take up 5‐hydroxytryptamine by an active as well as by a passive process and that the fluorescence observed after incubation with 5‐hydroxytryptophan is due to a high degree to decarboxylation into 5‐hydroxytryptamine.Noradrenaline and dopamine are apparently taken up by diffusion.Dopamine is taken up to some degree also by cells other than mast cells.