Activation and decay of the rat mast cells and its relationship to calcium uptake

Rat mast cells, stimulated for histamine release by compound 48/80 or lysosomal cationic protein, take up 45Ca2+ from he extracellular fluid. This uptake is inhibited by diisopropyl fluorophosphate, phenylmethylsulfonyl fluoride, and the inhibitors of energy metabolism. It was seen previously, when the release process is divided into two stages by activating the cells at 0 degrees C, the uptake of 45Ca2+ occurs during the release stage of the reaction. In the present studies, it was found that when cells activated at low temperatures were allowed to stand at 10 degrees C in the presence of 45Ca2+, the uptake of radioactive calcium increased in the first 15 min and then decreased to the levels of unstimulated cells. On the other hand, the release of histamine from the activated cells upon warming to 37 degrees C progressively decreased with an increase in time at 10 degrees C. These results suggest that during the decay of the active state the levels of intracellular exchangeable calcium pool are increased. For 45Ca2+ to be pumped out after the decay, there has to be net gain in intracellular calcium concentration during the first 15 min at 10 degrees C. The increase in membrane permeability to calcium appears to be due to the activation of a transient event.