Mast cell–lysosomal cationic protein interaction: effects of metabolic inhibitors and decay of activated cells on enhanced fluorescence of anilinonaphthalene sulfonate

It has been shown earlier that the interactions of the isolated rat peritoneal mast cells with cationic protein from rabbit neutrophil lysosomes (band 2 protein) can be studied using anilinonaphthalene sulfonate (ANS) as a fluorescent probe. In the present communication, binding of ANS dye to the mast cells interacting with band 2 protein (B2) under various conditions has been reported. The inhibition of histamine release by metabolic inhibitors was found to have no effect on enhancement of ANS fluorescence. On the other hand, inhibition of histamine release at high concentration of Ca2+ (14.4 mM) was accompanied by the decrease in enhanced fluorescence. In the presence of 7.2 mM of Sr2+, the release of histamine was enhanced with small but significant increase in ANS fluorescence. The cells heated to 42 °C partially lost their capacity to release histamine without the loss of enhanced fluorescence. The mast cells interacting with B2 at 10 °C for various time intervals showed time-dependent loss in histamine releasing capacity with concomitant loss in enhanced fluorescence. These studies suggest that the enhancement of ANS fluorescence is associated with the early events of the cell membrane caused by interaction of B2 with the cells. The extracellular cations significantly influence this early event.