**10. Metabolism and growth**

The change from anabolic to catabolic processes in fish exposed to various insecticides involves important alterations in intermediary metabolism and has important consequences for somatic growth. Changing levels of stress hormones – catecholamine and corticosteroids –, alterations in the ability of digestive enzyme biosynthesis and behavioral changes – hunter and forage behavior – are main factors influencing on the metabolism and growth of fish. For example, histopathological damage to liver, pancreas or hepato-pancreas and intestine can also reduce efficiency of food digestion in fish. Because, these tissues have critical role in regulation biochemical parameters, especially proteins, lipids and carbohydrates, hormones as well as in synthesis and secretion of digestive enzymes, are a target organs for toxicity of insecticides. So, the effect of insecticides on these organs can change metabolism of proteins, lipids and carbohydrates. The purpose of this section of the chapter is to describe briefly the metabolic activity known to be sensitive to various forms of insecticides toxicity. However, it has refused to more descriptions, because of breadth of the topic.

process of glycogen synthesis from glucose molecules, in which various enzymes such as involved. Hexokinase (HK), glucokinase, and glycogen synthase are key enzyme in the glycogenesis process. Studies show that interfere with activity of these enzymes associated with insecticides exposure of organisms can inhibit glycogen stored in liver (Rezg et al., 2006). Reduced glycogen contents in live and muscle of fish have been reported by some authors.

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Glycogenolysis is the catabolism of glycogen which leads to breakdown of glycogen to glucose and catalyzed by enzymes glycogen phosphorylase (GP), phosphoglucomutase (PGM), and glucose 6-phosphotase. Depletion of glycogen content in liver and muscle of fish during exposure to organophosphate insecticides was reported by many researchers (Ghosh, 1987;

In fish, catecholamine and corticosteroid hormones have an important role to promote gluconeogenesis. Cortisol is possible through increased levels activity of liver enzyme such as aspartate aminotransferase (AST), alanine aminotransferase (ALT) and tyrosine aminotrans‐ ferase (TAT) have a stimulatory effect on gluconeogenic mechanism.Since in the gluconeo‐ genesis process, glucose is produced from otherorganic molecules like pyruvate, lactate, glycerol, and aminoacids; elevated liver enzyme activity have an important role in the progress of the gluconeogenesis process. Although, pyruvate carboxylase, phosphoenolpyruvatecar‐ boxykinase (PEPCK), fructose 1,6bis-phosphatase, andglucose-6-phosphatase are key enzymes of this process, there are a limit information about their activities in the gluconeo‐

Glycolysis is a cascade of biochemical reactions by which a molecule of glucose is oxidized to two molecules of pyruvic acid and two high energy electron carrying molecules of NADH. Glycolysis can occur with or without oxygen. In the presence of oxygen, glycolysis is the first stage of cellular respiration. Without oxygen, glycolysis allows cells to make small amounts of ATP. Glycolysis is catalyzed by enzymes such as HK, phosphor-fructokinase (PFK), and

LDH is an enzyme participated in anaerobic pathway of carbohydrate metabolism. The increase of LDH activity is a diagnostic index widely used to recognize increases of anae‐ robic metabolism resulting from depletion of energy under anaerobic and environmental stress conditions.The increase of LDH activity can be attributed to the conversion of accu‐ mulated pyruvate into lactate which is transported through muscle to hepatopancreas and regenerated glucose and glycogen to supply energy fish exposed to insecticides. In other words, the increase of LDH activity in liver and muscle reflects a possible improvement

Proteins are vital ingredient involved in the architecture of the cell, which is the main source of amino acids for building up of new tissues and for the synthesis of biologically important molecules such as enzymes, hormones, etc as well as the source of energy for fish. Alterations

Nemcsok et al., 1987; Husain and Ansari, 1988).

genesis process in fish exposed to insecticides.

lactate dehydrogenase (LDH).

in tissue glycolytic capacity.

**12. Protein metabolism**

The most important factors decreasing fish growth consist of disorder in feeding behaviors, decrease in feeding rate, dysfunction in metabolism process and waste of energy to overcome the stress caused by insecticide exposure (Tripathi et al., 2003). For example, disorder in the metabolism of carbohydrates, proteins and lipids in various tissues, particularly liver of fish exposed to insecticides, may reduce their growth rates. Begum (2004) found out that protein and carbohydrate metabolism in the liver and muscle tissue is disrupted on the exposure to a carbofuran insecticide. In addition, exposure during embryonic or larval stage can result in behavioral abnormalities, such as decreased ability to capture prey after hatching, functional deficiencies or slowing of growth and finally death (Kuster, 2005; Viant et al., 2006; Arufe et al., 2007). These changes were observed in larvae and embryo of zebra fish (*Danio rerio*) in contact with endosulfan (Velasco-Santamaria et al., 2011), beta-cyprmethrin (Xu et al., 2010); paraoxon-methyl (Küster, 2005) and sevin (Todd and Leeuwen, 2002).
