EFFECTS OF 2,5-DI(TERT-BUTYL)-1,4-HYDROQUINONE ON INTRACELLULAR FREE CA2-SECRETION IN RBL-2H3 CELLS( LEVELS AND HISTAMINE)

The effects of 2,5-di(tert-butyl)-1,4-hydroquinone (DTBHQ) on the intr acellular free Ca2+ level ([Ca2+](i)) and histamine secretion leukemia (RBL-2H3) cells were (0.1-10 mu mol/l) alone induced increases in [Ca 2+](i) in a concentration-dependent manner. In cells sensitized with a nti-dinitrophenyl IgE, DTBHQ (10 mu mol/l) further increased the antig en (dinitrophenylated BSA)-induced Ca2+ response. In the absence of ex ternal Ca2+ with addition of 1 mmol/l EGTA, both DTBHQ (10 mu mol/l) a nd the antigen (10 mu g/ mi) induced transient increase in [Ca2+](i). In sensitized cells, both DTBHQ (10 mu mol/l) and antigen (10 mu g/ml) elicited histamine secretion, although the response was far stronger in the latter case. The DTBHQ-induced histamine secretion was markedly enhanced by addition of the protein kinase C activator, phorbol 12-my ristate 13-acetate (TPA) (10 ng/ml) whereas TPA alone did not cause an y increase. Moreover, DTBHQ enhanced the antigen-induced histamine sec retion. The results suggest that DTBHQ increases [Ca2+](i) and enhance s antigen-induced histamine secretion while DTBHQ alone does not cause as much histamine secretion as antigen, which support the idea that c alcium signals are necessary but are not sufficient for maximum histam ine secretion in RBL-2H3 cells.