Effect of intravenous nitroglycerin therapy on erythrocyte antioxidant enzymes

Intravenous nitroglycerin (GTN) has been used as an anti-ischemic agent for the therapy of unstable and post-infarction angina. Nitric oxide (^?NO) and S-nitrosothiols constitute the biologically active species formed via nitroglycerin bioactivation. Increased levels of reactive oxygen species can diminish the therapeutic action of organic nitrates by scavenging donated ^?NO and oxidizing tissue thiols important in nitrate biotransformation. Studies reported here show that the red cell activity of antioxidant enzymes, catalase and glutathione peroxidase, are significantly decreased after intravenous nitroglycerin treatment. Catalase activity decreased to and after 1 and 24?hr GTN infusion, respectively. Similarly, glutathione peroxidase activity decreased to and after 1 and 24?hr GTN infusion, respectively. The reported decrease in antioxidant enzyme activities can lead to an oxidant milieu and contribute to the generation of nitrate tolerance.