Effect of dialkyl phthalates on the degranulation and Ca2+ response of RBL-2H3 mast cells

We examined the effect of three dialkyl phthalates, di-n-butylphthalate (DBP), di-isobutylphthalate (DIBP) and di(2-ethylhexyl)phthalate (DEHP), on antigen-induced degranulation of RBL-2H3 mast cells. Exposure to 50-500 muM DBP, 50-500 muM DIBP, and 500 muM DEHP significantly potentiated antigen-induced beta-hexosaminidase release. Without antigen Stimulation, the phthalates did not cause any significant increase in degranulation. Next, we examined the Ca2+ response of RBL-2H3 cells after exposure to these phthalates. The cytosolic calcium ion concentration ([Ca2+](i)) of the cells clearly increased when the cells were stimulated with 50-500 muM DBP and 50-500 muM DIBP, and increased slightly when stimulated with 50-500 muM DEHP. Digital imaging fluorescence microscope analysis showed that the addition of DBP evoked Ca2+ oscillation in individual mast cells. Finally, we investigated the relationship between the DBP-sensitive Ca2+ stores and thapsigargin (TG)-sensitive, Ca2+ stores. A rise in [Ca2+](i) following challenge with DBP after TG was observed, and thus the DBP-sensitive and TG-sensitive Ca2+ stores in RBL-2H3 cells seem to be different. In conclusion, some dialkyl phthalates increase antigen-induced degranulation in RBL-2H3 cells dependent on the increase of [Ca2+](i). (C) 2002 Elsevier Science B.V. All rights reserved.