Magnesium influences incorporation of [3H]arachidonic acid in perfused rabbits hearts

Abstract

Ca(2+)-free perfusion of rabbit hearts produces a 50% loss of tissue Ca2+ and Mg2+ and results in reduced incorporation of arachidonic acid into tissue lipids. This work was undertaken to determine whether the reduced incorporation was specific for arachidonic acid and whether it was correlated to the loss of either (or both) cation(s). Single 170-pmol bolus doses of [3H]arachidonic or [3H]oleic acid were given to perfused hearts with or without Ca2+ in the perfusate. The experiment was terminated, and the lipids were extracted 1-15 min after administration of label. At all time points, significantly less arachidonate was incorporated into total tissue lipids in the absence of than in the presence of Ca2+. The presence or absence of Ca2+ had no effect on the incorporation of oleate. When [3H]arachidonate was administered to hearts perfused with buffer containing 104 mM Li+ and 35 mM Na+ (which reduces tissue Mg2+ by approximately 25% and increases tissue Ca2+ by approximately 35%), the incorporation into lipids was reduced from 0.882 +/- 0.0739 to 0.598 +/- 0.0722 pmol/mg lipid (P < 0.05; n = 6). The incorporation of [3H]oleate during 104 mM Li+ and 35 mM Na+ was not different from control. These data suggest that the incorporation of arachidonic, but not oleic, acid into tissue lipids is dependent on the tissue Mg2+ content.