ARACHIDONIC-ACID SUPPLEMENTATION ENHANCES HYDROGEN-PEROXIDE INDUCED OXIDATIVE INJURY OF NEONATAL RAT CARDIAC MYOCYTES

Objective: Selective fatty acid supplementation of non-myocardial cell s has been reported to enhance oxidative injury. The purpose of this s tudy was to extend this research by determining if supplementation of isolated cardiac myocytes with arachidonic acid increases myocyte sens itivity to H2O2 induced lipid peroxidation and cytotoxicity. Methods: Myocytes were supplemented with arachidonic acid by complexing it with calf serum and adding it to myocytes at a final concentration of 0, 5 0, or 100 mu M for 36 h. Myocytes were then exposed to 50 or 100 mu M H2O2 for 1 h and Lipid peroxidation and cytotoxicity were assessed by measuring thiobarbituric acid reactive substances and lactate dehydrog enase release into culture medium. To determine if unesterified arachi donic acid contributed to oxidative injury, 100 mu M arachidonic acid was added directly to cultured myocytes in serum-free buffer. Vitamin E and desferrioxamine were assessed for their ability to protect again st oxidative injury induced by unesterified arachidonic acid or H2O2. Results: Supplementation with 100 mu M arachidonic acid for 36 h incre ased the arachidonic acid content of phospholipids from 0.58(SD 0.06) to 0.90(0.19) nmol . nmol(-1) lipid phosphorus. A 1 h exposure to H2O2 induced lipid peroxidation and cytotoxicity in a concentration depend ent manner. Pretreatment of myocytes with 10 mu M vitamin E or 1 mM de sferrioxamine prevented H2O2 induced effects. Arachidonic acid supplem entation at 50 or 100 mu M significantly enhanced lipid peroxidation i nduced by 100 mu M H2O2, whereas cytotoxicity was increased only in my ocytes supplemented with 100 mu M arachidonic acid. Addition of uneste rified arachidonic acid directly to cultured myocytes caused marked cy totoxicity and lipid peroxidation which were prevented by vitamin E or desferrioxamine. Conclusions: Arachidonic acid supplementation of car diac myocytes modifies fatty acid content of phospholipids and enhance s the susceptibility of myocytes to H2O2 induced oxidative injury.