Inhibitors of arachidonic acid metabolism eliminate the increase in cytosolic free calcium induced by the mitogen concanavalin A in rat thymocytes

Using inhibitors of arachidonic acid (AA) metabolism, the possible involvement of AA products in the generation of [Ca 2+] i and the pH i rise induced by the mitogen concanavalin A (Con A) in rat thymocytes has been studied. The lipoxygenase inhibitor nordihydroguaiaretic acid (NDGA, 10 μM) and the phospholipase A 2 inhibitor bromophenacyl bromide (10 μM) eliminated the [Ca 2+] i signal induced by Con A; the cyclooxygenase blocker indomethacin also inhibited it. However, neither NDGA nor indomethacin suppressed the pH i rise stimulated by Con A. Exogenous AA induced an increase in [Ca 2+] i but not in the pH i. These results indicate that AA metabolites, probably of the lipoxygenase pathway, take part in the generation of the [Ca 2+] i response to the mitogen. In contrast, they appear not to be involved in the pH i rise evoked by Con A.