Pesticide applications have increased recently to control pests on farms, which eventually find their way into the aquatic environment [2], and pesticide pollution in the aquatic environment has drawn the attention of researchers and policymakers worldwide [3]. Generally, the use of pesticides has increased in the last few decades due to extensive use in agricultural and industrial processes; as a result, they are becoming threats to living organisms [4]. The increasing amount of industrial, agricultural, and domestic wastes into the aquatic environment has caused varying degrees of harmful effects on the aquatic organisms [1]. Pesticide contamination of aquatic ecosystems causes oxygen loss, fish sickness, and ultimately mass fish mortality. Fish have a propensity to use their numerous sections to accumulate toxins from their surroundings. On the other hand, xenobiotics, like pesticides, may cause physiological dysfunction in a number of biological systems, as well as changes in fish biochemistry, behavioral response, and hematological index [5]. They appear to have changed the metabolism of fish in several ways, some of which are deadly and more often sublethal. Stress and the effects of pesticides can alter hormones and enzymes, putting fish species at risk. Fish populations are more affected by long-term low-level exposure than by acute poisoning. Pesticide concentrations that are not high enough to kill fish are linked to subtle changes in physiology and behavior that hinder fish survival and reproduction [6]. On the other hand, alterations in fish ion concentrations, organic components, enzyme activity, endocrine activity, and chemo-regulators have all been linked to pesticides [7].

Serum enzyme activity measurements are widely used as a diagnostic tool in human medicine [8]. The use of enzymes is essential for the upkeep of an animal's metabolic functions and for the digestion of food. Their high specificity in terms of the type of reaction they catalyze and the substrate they use accounts for their exceptional efficiency. The permeability of cell membranes is affected by pollutants, xenobiotics, or toxicants that are macromolecules found in water bodies. Furthermore, these substances can alter the concentrations of reactants or cofactors, bind to enzymes, or indirectly impact enzyme function [9]. Fish exposed to industrial effluent show changed activity of hydrolytic enzymes, such as transaminases and esterases, due to its high conductivity and low dissolved oxygen level [10].

In toxicological research, enzymes are sensitive biomarkers because they can reveal early warning signs of potentially dangerous alterations in aquatic organisms that are suppressed in contaminated water [11]. Fish physiology may suffer relative damage from prolonged exposure to toxins; this damage can be quantified using metabolic enzymes, which are employed as clinical indicators [12]. In fish, enzymes are a valuable indicator for evaluating environmental exposures in vivo [13]. LDH, AST, ALP, ACP, and other enzyme assays can be utilized to detect abnormalities in fish [14]. Thus, evaluating the enzyme activity in the plasma of Coptodon guineensis exposed to butachlor in a laboratory setting is the aim of the current investigation.

Experimental Location and Fish

The African Regional Aquaculture Center, located in Buguma, Rivers State, is the branch office of the Nigerian Institute for Oceanography and Marine Research, where the study was conducted. At low tide, ponds yielded 360 Coptodon guineensis, of which 180 were juveniles and 180 were adults. The fish were transported to the lab in six 50-liter open plastic containers, where they were given seven days to acclimate.

Preparation of Test Solutions and Exposure of Fish

In this experiment, butachlor was utilized; it was bought from a store in Port Harcourt, Nigeria. The substance was given to two sizes of Coptodon guineensis in triplicate at concentrations of 0.00 mg/l (control), 0.05, 0.10, 0.15, and 0.20 mg/l with a 0.00 control. In every test tank, ten fish were put at random. There were fifteen days set aside for the exam. Every day, fresh water was added to the tanks. The fish were fed commercial feed twice a day at a body weight of 3%.

Analytical Procedure

Each experimental session ended with the caudal artery being punctured with a tiny needle to extract a 2 ml sample of fresh blood, which was subsequently placed into heparinized bottles. Immediately after, blood samples were centrifuged for 15 minutes at 5000 rpm. Separated plasma samples were pipetted into Eppendorf tubes and kept in a freezer at -20°C until being analyzed [15]. A Jenway visible spectrophotometer (Model 6405) with a universal microplate reader was used to read the results. The blood of the Coptodon guineensis exposed individuals had measurements of five enzymes: acid phosphatase (ACP), lactate dehydrogenase (LDH), aspartate amino transaminase (AST), alanine amino transaminase (ALT), and alkaline phosphatase (ALP). Since the Reitman and Frankel [16] method may be finished manually using a colorimetric end-point technique, it was employed to examine AST. However, ALP, ACP, and LDH were performed using the Huang et al. [17] technique.

Statistical Analysis

All the data were expressed using the mean and the mean's standard deviation. A statistical application called SPSS Version 22 was used to analyze the data. The means were divided using two-way ANOVA, and at 5% (P < 0.05), the two means were considered significant.

The physico-chemical parameters of water in experimental tanks of Coptodon guineensis exposed to butachlor are presented in Table 1. With the exception of DO, where lower values were found at greater chemical concentrations, the water quality metrics (Table 1) were all within the same range. Table 2 shows the effects of butachlor on the enzymes in the plasma of juvenile Coptodon guineensis. It was shown that as the herbicide concentration increased, the values of all the enzymes increased. The same trend was equally observed in the adult fish exposed to the chemical (Table 3).

Table 1: Physico-Chemical Parameters of Water in Experimental Tanks of Coptodon guineensis Exposed to Butachlor.

Means within the same column with different super scripts are significantly different (P<0.05).

Table 2: Activities of Dehydrogenase, Phosphatase, and Tranminases in Coptodon guineensis Juveniles Exposed to Butachlor.

Means within the same column with different super scripts are significantly different (P<0.05).

Table 3: Activities of Dehydrogenase, Phosphatase, and Tranminases in Coptodon guineensis Adults Exposed to Butachlor.

Means within the same column with different super scripts are significantly different (P<0.05). 

In fish, ACP and ALP activity are helpful indicators of toxicant stress. Any damage or malfunction in the test organs indicates a shift in phosphatase activity. According to the study, Coptodon guineensis plasma treated with various butachlor concentrations increased. It is possible to explain an increase in acid and alkaline phosphatase activity by the tissue refocusing its energy breakdown efforts on the phosphatase system rather than the usual ATPase system. Pesticides decrease glycogen levels and increase phosphorylation activity [18]. In the event of a decreased ATPase system, activated phosphatases can catalyze the release of inorganic phosphates from phosphate esters, which can result in phosphorylation. In the current investigation, herbicide exposure altered the activities of the ACP and ALP. Cellular damage triggers an increase in the activity of the lysosomal enzyme ACP [19]. The enhanced ACP and ALP activity could be due to an accelerated rate of enzyme turnover under pesticide exposure. These phosphatases are active at specific pH levels; they are also referred to as phosphomonoesterases. The way that ACP and ALP change depends on the period, pesticide value, and concentration. Changes brought about by pesticide dichlorvos toxicity resulted in higher levels of these two enzymes, ACP and ALP, in fish Labeo rohita [20]. However, the elevation of ALP is significantly less important than that of ACP.

In experimental settings, problems in animals are usually identified by measuring various enzymes, including AST, ALT, and LDH [21]. The presence of the non-plasma-specific enzymes ALT, AST, and LDH in the blood may provide specific information about organ dysfunction because these enzymes are present in the tissue cells of the liver, heart, gills, kidneys, muscles, and other organs. Several investigations have documented variations in these enzymes' activities due to the effects of pollutants or poisons on various fish organs in various species [22]. Numerous soluble enzymes that are present in blood serum have been proposed as useful indicators of stress. Measurements of serum ALT, AST, and LDH activity can be used to diagnose fish illnesses and detect tissue damage associated with environmental exposure. An increase in these enzyme activities in the serum or extracellular fluid, a sensitive sign of even modest cellular damage, indicates stress-related tissue degradation [23]. All of the enzymes examined in this experiment were found in higher concentrations in the plasma of Coptodon guineensis treated with butachlor. This data is consistent with the findings of Gabriel et al. [24], who found that African catfish (Clarias gariepinus) treated with cypermethrin had increased blood ALT, AST, and LDH activity. After being exposed to cypermethrin, the fish Rhamdia quelen [25] and Labeo rohita [26] had a significant increase in plasma ALT, AST, and LDH activity. Nile tilapia were given sub-acute dosages of deltamethrin and pyrethroid for a duration of 28 days, and this again resulted in an increase in serum ALP [27]. These researchers came to the conclusion that the possible explanation of the blood surge in this enzyme may be hepatic necrosis and the resulting leaking of this enzyme into the bloodstream. Because of the manner that toxicants impact hepatocytes, elevated levels of ALT, AST, and LDH typically signify liver hypofunction and degeneration. This is due to the fact that tissue degradation results in the release of cellular enzymes into the blood plasma [28, 29]. Thus, the fact that increases in these enzyme activities in Coptodon guineensis serum are primarily caused by the leaking of these enzymes from the liver cytosol into the bloodstream as a result of liver damage brought on by metals and pesticides illustrates the hepatotoxic effect of toxicants [30]. According to Tamas et al. [31], elevated blood levels of these enzymes are typically suggestive of disease and liver necrosis in animals. Blood levels of ALT, AST, and LDH may rise as a result of hepatic cellular injury [32].

In Coptodon guineensis juveniles and adults, sublethal butachlor doses can result in enzymatic breakdown and other toxicological effects. The biochemical profiles of blood can offer significant information on the internal environment of an organism, as blood is the first organ to be affected by unfavorable environmental changes. The results of this investigation provided support for the hypothesis that alterations in the plasma enzyme activity of fish exposed to pesticides were a biochemical manifestation of the harmful effects of toxicants. When contrasted with the control group that did not receive any pesticide exposure, fish treated with pesticides showed greater increases in all plasma enzyme parameters. Finally, variations in the parameters of plasma enzymes can serve as quick and accurate markers for tracking the effects of toxicants on aquatic life and eventually the ecosystem in its entirety. These indicators are indicative of toxicant-induced target tissue damage and dysfunction.

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