Effects of newly arachidonic acid metabolites on microsomal Ca⁺⁺ binding, uptake and release

The 5,6- 8,9-; 11,12- and 14,15-epoxyeicosatrienoic acids and their respective hydration products, the vic-doisl, recently reported as metabolites of arachidonic acid in rat liver microsomes, were examined for effect on release of 45Ca from canine aortic smooth muscle miscrosomes. At 10^-6 M, the diols had no effect, but the 5,6-; 11,12- and 14,15-epoxyacids increased the loss of ⁴⁵Ca. Further studies with the 14,15-epoxyacid demonstrated a dose-dependent decrease of Ca⁺⁺ uptake (ATP present) in canine aortic microsomes in 0.03 mM Ca⁺⁺, whereass Ca⁺⁺ binding (ATP absent) was not affected. Ca⁺⁺ uptake, binding and release in rat liver microsomes was similarly affected by the 14,15-epoxyacid, the major epoxyeicosatrienoic acid derivative produced by rat liver miscrosomal incubations. It is suggested that a alterations in Ca⁺⁺ metabolism might be a possible mechanism of actions for these derivatives of arachidonic acid.