We examined the effect of pervanadate on the activation of rat basophilic leukaemia (RBL-2H3) cells. The pervanadate, generated from a combination of H2O2 and vanadate (Vi), induced concomitantly protein tyrosine phosphorylation, formation of inositol 1,4,5-trisphosphate (IP3), an increase in [Ca2+]i, and histamine secretion in RBL-2H3 cells. These effects were clearly dependent on the ratio of H2O2/Vi. The secretion of histamine, IP3 formation, and sustained increase in [Ca2+]i were effectively induced by treatment of the cells with the pervanadate produced from 1 mM H2O2 and 1 mM Vi. These effects mimic the stimulatory effects of an antigen (dinitrophenylated BSA) on Ca2+ signals, histamine secretion and morphological changes. Protein tyrosine phosphorylation, formation of IP3 and transient increase in [Ca2+]i were markedly induced by the pervanadate produced from 3 mM H2O2 and 1 mM Vi. However, histamine secretion induced by the pervanadate was very low. After the pervanadate from 3 mM H2O2 and 1 mM Vi was treated with catalase, it was able to induce the [Ca2+]i increase and histamine secretion as much as the antigen did. This indicates that pervanadate from a lower H2O2 concentration (1 mM H2O2/1 mM Vi) and catalase-treated pervanadate from a higher H2O2 concentration (3 mM H2O2/1 mM Vi) are able to mimic the activity that was caused by cross-linking of IgE receptors with antigen. The present results also demonstrate that protein tyrosine phosphorylation seems to have a crucial role in Ca2+ entry from the external medium, and that a sustained [Ca2+]i increase is an important step for histamine secretion in RBL-2H3 cells.

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