Figen Esin Kayhan et al./ Elixir Pollution 110 (2017) 48560-48563 48560 The 2,4-D Herbicidal Effect of Defense Enzyme Activities and AChE Levels in Liver and Gill Tissues of Xiphophorus hellerii (Swordtail fish) Figen Esin Kayhan * , Gamze Tuğçe Turan, Güllü Kaymak, Cansu Akbulut and Nazan Deniz Yön Ertuğ Marmara University, Science and Letters Faculty Department of Biology, İstanbul, Turkey. Introduction Fish are vulnerable to alteration of environmental factors caused by the introduction of industrial wastes, heavy metals, pesticides, oils, pills and other agents that directly affect the aquatic ecology. Toxic effects of pesticides on the biochemical and physiological systems of a fish can be determined through the study of malondialdehyde levels (MDA) and acetylcholine esterase enzyme activity (AChE), among other methods [1]. Biochemical biomarkers can provide information about the process of pesticide detoxification. When in contact with an organism, the toxic agent can be biotransformed by enzymes, which act to make the xenobiotic substance a less toxic compound and facilitate its excretion. Lipid peroxidation may be the first step of cellular membrane damage and can be induced by environmental pollutants as herbicides. Organisms have both enzymatic and non-enzymatic antioxidant defenses against reactive oxygen species (ROS) [2]. One of the first enzymes that act in defense against ROS is superoxide dismutase (SOD). It catalyses the conversion of reactive superoxide anions (O 2 .- ) to hydrogen peroxide (H 2 O 2 ), which is subsequently detoxified by catalase (CAT) and glutathione dependent peroxidase (GPx). GPx catalyses the metabolism of H 2 O 2 to water involving a concomitant oxidation of reduced glutathione (GSH), one of the most important non-enzymatic antioxidants in the cell [3]. The activity of AChE is another biochemical biomarker normally used to monitor aquatic environments mainly contaminated by pesticides. This enzyme can be inhibited by different types of agrochemicals [4]. Pesticide pollution can be observed in increasing amounts in water and soil as a result of its uncontrolled and unaware usage in many countries. These pesticides can be removed by rain and irrigation water. The number of scientific studies show that the agricultural usage of pesticides have negative ecological effects and toxic effects on living things in the medium, environment in addition to the effects on immune systems and various tissues, which respectively increases day by day [5-8]. Two groups of herbicides can be divided in terms of creation of oxidative stress: The first is known to be directly responsible for the enhancement of free radical generation, entering redox cycles and constantly generating ROS. The second group of herbicides consists of several classes of compounds known to be mainly inhibitors of antioxidant enzymes, such as SOD and CAT [2]. 2,4-Dichlorophenoxyacetic acid (2,4-D) has been the most commonly used acidic phenoxy herbicide in agriculture and forestry since 1940. 2,4-D is one of the most common and most toxic herbicides. 2,4-D has a notorious past. It was one of the two chemicals in the defoliants Agent Orange and Agent Purple. It was also one of the two chemicals in Agent White. The toxicity of 2,4-D depends on its chemical forms, including salts, esters, and an acid form. The ester forms of 2,4-D can be highly toxic to fish and other aquatic life. 2,4-D generally has moderate toxicity to birds and mammals, is sorely toxic to fish and aquatic invertebrates, Herbicidal activity of 2,4-D may also be due to an increase in the production of ROS. The objective of this study is to understand the effects of the herbicide 2,4-D on swordtail fish tissues by using a set of biochemical markers. To this aim, CAT and AChE enzyme activities and MDA levels were measured using spectrophotometric methods in liver and gill tissues of Swordtail fish (Xiphophorus hellerii Heckel, 1848). Material and Method The applied doses of 2,4-D were prepared using commercial 2,4-Dichlorophenoxyacetic acid salt emulsions. X. hellerii was obtained from local commercial aquarists. The animals were acclimatized for two weeks in stock tanks under laboratory conditions. Millipore water was used in this experiment. During the acclimatization period, fish were fed ad libitum with pellet twice a day. The fish were randomly selected and divided into four experimental groups, arranged Tele: 9002163464553 E-mail address: figenesink@gmail.com © 2017 Elixir All rights reserved ARTICLE INFO Article history: Received: 12 July 2017; Received in revised form: 19 September 2017; Accepted: 29 September 2017; Keywords Oxidative stress in fish, Herbicide, AChE, Antioxidant systems. Elixir Pollution 110 (2017) 48560-48563 Pollution Available online at www.elixirpublishers.com (Elixir International Journal) ABSTRACT In the present study, herbicide 2,4-D was investigated for its potency to induce oxidative stress and its effects on antioxidant systems in gill and liver tissues of ( Xiphophorus hellerii). Animals were exposed to sublethal doses of 2,4-D for 96 hours except for the control group. Protein, malondialdehyde, catalase and acetylcholine esterase enzyme activity (AChE) were determined using spectrophotometric methods. The results show that protein levels were reduced in all experiments when compared to control group. Levels of malondialdehyde were increased in each group. Catalase enzyme activity was significantly decreased in all groups. In addition, an increased AChE activity was observed. © 2017 Elixir All rights reserved.