Correspondence: Mehmet Aslan, Yuzuncu Yil University, Medical Faculty, Department of Internal Medicine, 65000, Van, Turkey. Tel: + 90 (432) 215 0473. Fax: + 90 (432) 216 7519. E-mail: m.aslan301@mynet.com (Received 23 August 2013; accepted 7 December 2013) ORIGINAL ARTICLE Serum prolidase enzyme activity and oxidative stress levels in patients with acute hemorrhagic stroke HAYRI ˙ YE GONULLU 1 , MEHMET ASLAN 2 , SEVDEGUL KARADAS 1 , CELAL KATI 3 , LATI ˙ F DURAN 3 , AYSEL MI ˙ LANLIOGLU 4 , MEHMET NURI ˙ AYDIN 4 & HALI ˙ T DEMI ˙ R 5 Departments of 1 Emergency Medicine and 2 Internal Medicine, Medical Faculty,Yuzuncu Yıl University,Van, 3 Department of Emergency Medicine, Ondokuz Mayıs University, Samsun, 4 Department of Neurology, Medical Faculty,Yuzuncu Yıl University,Van, and 5 Department of Chemistry , Faculty of Science and Art,Yuzuncu Yıl University ,Van, Turkey Abstract Background. It has been indicated that oxidative damage contributes to secondary brain injury in both ischemic and hemorrhagic stroke patients. Collagen is a major component of the extracellular matrix, and prolidase plays a role in collagen synthesis. The aim of this study was to evaluate the serum prolidase activity, nitric oxide (NO) levels, total anti- oxidant capacity (TAC) and total oxidant status (TOS) in patients with acute hemorrhagic stroke. Methods. Twenty-five patients with acute hemorrhagic stroke and 25 controls were enrolled. Serum prolidase activity, catalase activity, NO levels, TAC and TOS were measured spectrophotometrically. Oxidative stress index (OSI) was calculated. Results. Serum TAC levels and catalase activity were significantly lower in acute hemorrhagic stroke patients than controls (both, p  0.001), while NO levels, TOS levels, OSI values and prolidase activity were significantly higher (all, p  0.01). When patients with acute hemorrhagic stroke were divided according to gender, no differences were observed between females and males in respect to serum prolidase enzyme activity, NO levels, TAC levels, TOS levels and OSI values (all, p  0.05). Conclusions. Findings from the study suggest an association between increased oxidative stress levels, decreased antioxidant levels and increased prolidase enzyme activity in patients with acute hemorrhagic stroke compared with controls. More studies are needed to elucidate mechanistic pathways on oxidative stress in patients with acute hemorrhagic stroke. Key Words: Acute hemorrhagic stroke, prolidase activity, catalase activity, nitric oxide, total antioxidant capacity, total oxidant status, oxidative stress index Introduction Intracerebral hemorrhage is a common and often fatal subtype of stroke [1]. Stroke is recognized as one of the leading causes of death and severe neurological disability worldwide [2]. A stroke occurs when blood vessels that deliver oxygen to the brain either rupture or become clogged causing brain/nerve cells to die [3]. The brain is particularly vulnerable to oxidative stress because of its high rate of oxidative metabolic activity and intense production of reactive oxygen species (ROS) [4]. The elevation of the ROS leading to oxidative stress appears to play an important role in the patho- genesis of ischemic [5] and hemorrhagic [6] brain injury. It has been indicated that oxidative damage contributes to secondary brain injury in both ischemic and hemorrhagic stroke patients [7]. Antioxidant treatment reduces neurological deficits in a rat intracerebral hemorrhage model [8]. Collagen type 1 fibers together with the collagen type 3 fibers compose up to 90% of the total arterial collagen and are important for the strength of arterial walls [9]. Collagen type I is mainly confined to the adventitia and thus defects in the collagen gene are obvious candidate etiologies for hemorrhagic strokes, such as intracranial aneurysms [10]. The extracellular matrix (ECM) consists of collagens, proteoglycans, and glycoproteins. The ECM is degraded by matrix metalloproteinase (MMPs) resulting in the release of a large amount of imidotripeptides with C-terminal proline or hydroxyproline [11]. Prolidase is a special type of MMP and is a manganese-dependent cytosolic Scandinavian Journal of Clinical & Laboratory Investigation, 2014; 74: 199–205 ISSN 0036-5513 print/ISSN 1502-7686 online © 2014 Informa Healthcare DOI: 10.3109/00365513.2013.873949