Toluene (C7H8, monomethylbenzene, methylbenzene, phenylmethane) is an aromatic hydrocarbon solvent widely used in many industries such as plastics, gasoline and cosmetics industries. Toluene; it is used as a component of paint, polish, adhesive, ink and cleaning fluids. It is also used for different purposes in the rubber and wood industries, dry cleaning, automotive, aviation and cleaning industries [1, 2]. It has been reported that toluene is also used in the cosmetic industry [3]. Toluene is lighter than water in the liquid state, three times heavier than air in the vapor phase, and has a high affinity for lipids. It is flammable. The temperature at which it can evaporate to form a flammable mixture in air is 4.4°C [4]. Since it is found in many products used in daily life, toluene can be easily exposed. Toluene can affect humans through inhalation or skin. Safe exposure limits for this substance are generally between 10 and 100 ppm. The limit of immediate danger to life and health (IDLH) is defined as 500 ppm [4, 5]. People who take toluene-based products by inhalation (abuse) are exposed to doses of several thousand ppm of this substance [6, 7]. Toluene; it causes various adverse effects depending on the amount of exposure. Doses of 200 ppm cause fatigue, headache, and slowing of reflexes, while doses of 600 ppm and above cause confusion, and doses close to 800 ppm cause euphoria [2, 8].
Resveratrol (3,5,4'-trans-trihydroxystilbene) (RES) is a polyphenolic phytoalexin belonging to the stilbens family. This substance, synthesized from phenylalanine, is abundant in grape skin and seed [9, 10]. It is a compound naturally produced in about 72 different plant species (blueberries, raspberries, blackberries, peanuts and legumes etc) [11, 12]. Plants synthesize RES in response to stress. Use in cases of injury, as a shield against ultraviolet radiation, fungal infections and other threats [13, 14]. RES has two phenol rings (monophenol and diphenol) linked by a double styrene bond. It is found in plants in both cis and trans isomeric forms (Fig. 1). It participates in the removal of free radicals and chelate formation reactions with metals with the 3 OH groups it contains [15–17].
RES attracted the attention of scientists after it was discovered from the plant Veratum grandiflorum. To date, many publications have been made about RES. In recent years, the fact that it has been shown to be effective on some important pathways in cancer has further increased the importance of this molecule. It has gained value among molecules with high medical value due to its anti-inflammatory, antidiabetes, antioxidative, antiviral, antitumor properties [18–20]. In-vivo and in-vitro studies have revealed the importance of RES [17, 21–24].
Lactate dehydrogenase (LDH) (EC 1.1.1.27) is an important enzyme in the anaerobic metabolic pathway, widely found in all mammalian cells [25]. Located in the cytoplasm of the cell. While it converts lactate to pyruvate by reduction of NAD to NADH, it also converts pyruvate to lactate using NADH. LDH is a tetrameric protein. 5 isoenzymes have been identified. LDH1 and LDH2 are seen in kidney, heart, brain and erythrocytes, while LDH3 and LDH4 are seen in lymph nodes, endocrine glands, spleen, thymus, leukocytes, platelets and non-pregnant uterine muscle. LDH4 and LDH5 are more common in liver and skeletal muscle. In case of tissue damage or injury, their amount in plasma increases [26]. It has also been shown by Friberg et al. [27] that this enzyme is frequently overexpressed in tumors. The amount and activity of the LDH enzyme increases in many diseases such as liver, kidney and heart, pulmonary embolism, muscular dystrophy, pancreatitis, anemia, meningitis, ischemia, pneumonia, bone fractures, muscle injuries and infections. A decrease in the amount of LDH is a rare condition [28].
Therefore, the aim of the study was to examine the effect of toluene exposure on LDH activity in blood, liver and muscle tissue of male rats and to investigate the protective effect of RES on LDH.