Uptake of 5‐Hydroxytryptamine by Rat Peritoneal Mast Cells in vitro

The mechanism of 5‐hydroxytryptamine (5‐HT) uptake by rat peritoneal mast cells in vitro was studied under different incubation conditions. The uptake reached a saturation level even at low concentration of exogenous 5‐HT resulting in a concentration ratio of more than one thousand times. The uptake during the first hour was more rapid when compared with the slow uptake during succeeding hours. The uptake was dependent on temperature and calcium and magnesium ions. Addition of glucose to the medium did not accelerate the uptake which also was unaffected by pH alteration from 6.0 to 7.4. The proposed active uptake mechanism Tor 5‐HT was supported by the results obtained with metabolic inhibitors; those belonging to the group of uncouplers of oxidative phosphorylation effectively inhibited the uptake while sodium cyanide and sodium azide were without significant effect. Results obtained further indicated that 5‐HT at high exogenous concentrations may passively diffuse into the mast cells.