INHIBITION OF HISTAMINE-RELEASE FROM RBL-2H3 CELLS BY PROTEIN-SYNTHESIS INHIBITORS

Effects of cycloheximide, an inhibitor of protein synthesis, on histam ine release from RBL-2H3 cells were examined. RBL-2H3 cells sensitized by rat antiserum to ascaris extract were challenged by the antigen, a nd histamine release during a period of 30 min was measured. Pretreatm ent with cycloheximide (1 mu g/ml) for 1 h significantly inhibited the antigen-induced histamine release (36% inhibition). The cycloheximide -induced inhibition of histamine release was abolished when the cells were further incubated in the absence of cycloheximide for 2 h. Pretre atment with puromycin (3 and 10 mu g/ml), an inhibitor of protein synt hesis, or actinomycin D (0.1-1 mu g/ml), an inhibitor of DNA-dependent RNA synthesis, also inhibited the antigen-induced histamine release i n a concentration-dependent manner. Both ionomycin- and thapsigargin-i nduced histamine release were also inhibited by pretreatment with cycl oheximide. Measurement of intracellular Ca2+ levels using quin 2 revea led that cycloheximide inhibits the increase in Ca2+ levels induced by the antigen, ionomycin or thapsigargin. These results suggest that hi stamine release induced by the antigen, ionomycin and thapsigargin in RBL-2H3 cells is mediated by protein(s) which is newly synthesized and inactivated rapidly, and the newly synthesized protein(s) is involved in the increase of intracellular Ca2+ levels induced by these stimula nts.