Cross-linking of surface immunoglobulin on B lymphocytes induces both intracellular Ca 2+ release and Ca 2+ influx: Analysis with indo-1

Abstract

The new Ca 2+-probe indo-1 has a high fluorescence intensity, which allows low intracellular dye loadings. Stimulation of indo-1-loaded mouse B cells with anti-Ig antibodies provoked rapid rise of free cytoplasmic Ca 2+ from 100 mM to >1 μM, followed by a decline to a plateau at 300–400 nM. The initial rapid rise was not detected in quin2-loaded cells, presumably due to the Ca 2+-buffering effects of the dye. The sustained Ca 2+ increase was due to influx, whereas the initial rise was caused by release from intracellular stores. The magnitudes of Ca 2+ release and inositol trisphosphate release were closely correlated. Concanavalin A does not provoke inositol trisphosphate release in mouse B cells. It did not induce a rapid initial Ca 2+ rise in indo-1-loaded B cells either, but only a sustained increase to 200–300 nM. Finally, Ca 2+ influx induced by both anti-Ig and concanavalin A were not affected by membrane depolarization