Effect of vitamin E on arachidonic acid-release in rat peritoneal macrophages.

We have previously reported on suppression of the PGE2 production in PMA- and calcium ionophore A23187-stimulated macrophages isolated from vitamin E-treated rats. To further study the mechanism, we examined the effect of vitamin E on phospholipase A2 activity in both intact macrophages and cell-free homogenates measuring the release of [14C]arachidonic acid. In macrophages from vitamin E-treated rats, arachidonic acid release in intact cells as stimulated with PMA and calcium ionophore A23187 was hardly detected. In the cell-free homogenates, increase in phospholipase A2 activity of cytosol and particulate fractions by PMA and A23187 was partially suppressed. In unstimulated macrophages, most of phospholipase A2 was recovered in the cytosol fraction. The partially purified cytosolic phospholipase A2 showed a molecular mass 95 kDa on TSK gel G3000SW gel-filtration and on Western blot analysis using anti-rabbit platelet phospholipase A2 monoclonal antibody RHY-5. The activity of cytosolic 95 kDa phospholipase A2 was not inhibited in vitro by vitamin E. From these results, it was suggested that vitamin E needs intact macrophages to suppress arachidonic acid release.