Research Article Effect of the Antihypertensive Drug Enalapril on Oxidative Stress Markers and Antioxidant Enzymes in Kidney of Spontaneously Hypertensive Rat G. Chandran, 1 K. N. S. Sirajudeen, 1 Nik Syamimi Nik Yusoff, 1 M. Swamy, 1 and Mutum S. Samarendra 2 1 Department of Chemical Pathology, School of Medical Sciences, Universiti Sains Malaysia, Health Campus, 16150 Kubang Kerian, Kelantan, Malaysia 2 Department of Pathology, School of Medical Sciences, Universiti Sains Malaysia, Health Campus, 16150 Kubang Kerian, Kelantan, Malaysia Correspondence should be addressed to K. N. S. Sirajudeen; sirajuden@usm.my Received 12 February 2014; Revised 14 July 2014; Accepted 14 July 2014; Published 28 August 2014 Academic Editor: Kota V. Ramana Copyright © 2014 G. Chandran et al. Tis is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Oxidative stress has been suggested to play a role in hypertension and hypertension induced organ damage. Tis study examined the efect of enalapril, an antihypertensive drug, on oxidative stress markers and antioxidant enzymes in kidney of spontaneously hypertensive rat (SHR) and N -nitro-L-arginine methyl ester (L-NAME) administered SHR. Male rats were divided into four groups (SHR, SHR+enalapril, SHR+L-NAME, and SHR+enalapril+L-NAME). Enalapril (30 mg kg −1 day −1 ) was administered from week 4 to week 28 and L-NAME (25 mg kg −1 day −1 ) was administered from week 16 to week 28 in drinking water. Systolic blood pressure (SBP) was measured during the experimental period. At the end of experimental periods, rats were sacrifced; urine, blood, and kidneys were collected for the assessment of creatinine clearance, total protein, total antioxidant status (TAS), thiobarbituric acid reactive substances (TBARS), superoxide dismutase (SOD), and catalase (CAT), as well as histopathological examination. Enalapril treatment signifcantly enhanced the renal TAS level ( < 0.001) and SOD activity ( < 0.001), reduced the TBARS levels ( < 0.001), and also prevented the renal dysfunction and histopathological changes. Te results indicate that, besides its hypotensive and renoprotective efects, enalapril treatment also diminishes oxidative stress in the kidneys of both the SHR and SHR+L-NAME groups. 1. Introduction Hypertension is a global chronic health condition in which systemic arterial pressure is persistently elevated. It is of great public concern as prolonged, uncontrolled hypertension leads to cardiovascular diseases and organ damage including the kidneys, resulting in nephropathy, chronic renal disease, and ultimately renal failure [1]. Tis makes it the leading behavioural and physiological risk factor for attributable deaths, accounting for 13% of global deaths [2]. Te pathogenesis of essential hypertension is multifacto- rial and highly complex as various factors modulate the blood pressure in the body [3]. In this respect, free radical medi- ated oxidative damage has been proposed as an important predisposing pathogenic mechanism in the development and progression of hypertension and its complications including organ damage [4, 5]. Free radicals and their metabolites, reactive oxygen species (ROS), are constantly formed in the body by several mechanisms. Tese substances, being reac- tive, can cause oxidative damage to biological molecules. Te body possesses antioxidant systems that are very important to protect cellular components from free radical induced oxida- tive damage. Tese consist of nonenzymatic and enzymatic systems including SOD and CAT [6]. Under physiological conditions, ROS produced in the course of metabolism are contained by the body’s antioxidant defence mechanism. When these defence mechanisms are inadequate, either due to increased ROS production or diminished antioxidant Hindawi Publishing Corporation Oxidative Medicine and Cellular Longevity Volume 2014, Article ID 608512, 10 pages http://dx.doi.org/10.1155/2014/608512