Objective: The aim of this study was to investigate the effects of acute and chronic administrations of Nw nitro-L-arginine (L-NNA), a non-spesific NOS inhibitor, on plasma levels of Nitrite/Nitrate (NOx) and Malondialdehyde (MDA) in rats.

Material and Method: A single dose L-NNA (aL-NNA, 25mg/kg i.p.) was administered and systolic blood pessure (SBP), NOx were measured at 1, 3, 24 hours. MDA were measured at 1, 24 hours. L-NNA was administered orally dose of 15mg/100ml/day (d-LNNA) and 45mg/100ml/day (yLNNA) for 2 weeks. dL-NNA was divided into 3 subgroups: SBP, NOx and MDA levels were determined at the end of experiments in dL-NNA0 subgroup and also 24 (dL-NNA24) and 48 hours (dL-NNA48) after the cessation of chronic L-NNA administration. yL-NNA group was not divided subgroups.

Results: In the aL-NNA, SBP was higher at first and third hour which declined to the basal values at 24th hour. NOx was not change at one hour but decreased at third hour and returned to the basal levels at 24th hour. MDA were higher at first hour and remained high at 24th hour. In the long term L-NNA treated groups; both doses of L-NNA caused significant increase in SBP but NOx levels were increased only in the yL-NNA. MDA levels of dL-NNA0 were not changed but there was a significant increase in the MDA levels of the dL-NNA24, dL-NNA48 and yL-NNA.

Conclusion: Results from this study indicates that acute L-NNA application causes oxidative stress but its chronic applications caused the same effect only at high doses. ©2008, Fırat University, Medical Faculty