A further characterization of acridine-photosensitized inhibition of mast cell degranulation.

The purpose of this study was to further characterize acridine-photosensitized inhibition of mast cell degranulation. Acridine plus UVA radiation (320-400 nm) inhibited degranulation in response to antigen in IgE-sensitized rat serosal mast cells and in response to concanavalin A, which acts by a mechanism similar to antigen-IgE challenge. Removing oxygen from the incubation medium prevented the acridine-photosensitized inhibition of mast cell degranulation in response to 48/80. Acridine plus UVA radiation did not decrease mast cell ATP content, thus excluding inhibition of ATP production as a mechanism for photosensitized inhibition of mast cell degranulation. Although the viability of mast cells, as determined by uptake of trypan blue, was not affected 3 h after treatment with acridine plus UVA radiation, viability decreased by 6 h, and by 22 h 44% of the cells were nonviable. These results indicate that degranulation of mast cells by a variety of agents is inhibited by UVA plus acridine treatment, and that photosensitization requires oxygen and occurs before cytotoxicity.