Inositol 1,4,5-trisphosphate- and arachidonic acid-induced calcium mobilization in T and B lymphocytes.

Inositol triphosphate (IP3) formation and increase in intracytoplasmic calcium are mediators of signal transduction in lymphocytes. It has been proposed that IP3 induces Ca2+ release from intracellular stores. It is in order to study the relationship between these two events that we have analyzed the effect of IP3 addition on Ca2+ mobilization in permeabilized resting T and B lymphocytes, EBV-B lymphocytes, and HTLV1-T lymphocytes. IP3 induces a rapid and significant release of Ca2+ from the endoplasmic reticulum in a dose-dependent manner. Ca2+ release is more sensitive to IP3 addition in cycling cells (EBV-B lymphocytes and HTLV1-T lymphocytes) than in resting T and B lymphocytes. Arachidonic acid (AA) induces Ca2+ release from the endoplasmic reticulum (ER) in a manner similar to that of IP3. Neither component has an effect on Ca2+ accumulated in mitochondria, and they have no additive effects suggesting that they act on a similar Ca2+ pool. These results directly demonstrate that in T and B human lymphocytes IP3 mobilizes Ca2+ from ER as in other cellular systems and that other potential second messengers, namely AA, could play a significant role in the internal mobilization of calcium during T and B lymphocyte activation.