Effects of Pesticides on Total Protein Content of Different Organs of Oreochromis niloticus (Linnaeus, 1758)

Pesticides including OPs (malathion 57% EC and chlorpyrifos 40% EC) and synthetic pyrethroid (lambda- cyhalothrin 2.5% EC) of STEDEC Technology Commercialization Corporation of Pakistan (Pvt. Limited) were purchased from the market. For the preparation of different concentration of pesticides Charle’s equation (C1 V1= C2 V2) was used for the dilution of the stock solution, where C1 V1 represent the initial concentration and volume of the pesticides (stock solution) and C2 V2 are the required concentration and volume of the pesticides.

Oreochromis niloticus (mean weight (17.8±0.2 g) and total length (12.12±0.6cm)) were purchased from the hatchery of Chilya Thatta and were transported to the Laboratory of Toxicology, University of Karachi in a plastic bag containing oxygenated water. An aerated glass aquarium (volume range: 57 x 30 x 30 cm) was used for the maintenance of the test fishes and were acclimatized for 15 days in dechlorinated tap water under the laboratory condition in natural light and dark period. Throughout the acclimatization period, the water in the aquarium was replenished and aerated regularly by an electric air pump. Fish were fed with commercial pellets of Oryza Pvt. Limited (40% protein) provided daily at 2% of body weight. The physicochemical properties of water were measured according to the methods mentioned in APHA (2005) and recorded as follows; temperature 26±0.7oC, dissolved oxygen 5.5 ± 0.5 mg/L, ammonia (NH3) 1± 0.1 mg/L, nitrate 1.2 ± 0.4 mg/L, and pH 7.08 ± 0.2. After the acclimatization period, ten fish were transferred to each aquarium (25 x 25 x 25 cm) containing 10 L of water so as to reduce the stress. The LC50 was determined by Finney (1971) method and then its 1/4th part was used for biochemical study. Fishes were exposed to the sub-lethal concentrations of malathion (1.425 ppm), chlorpyrifos (0.125 ppm) and lambda-cyhalothrin (0.0039 ppm) for 24h and 48h. Control groups were also run in water without the addition of pesticides. The experiment was performed in triplicates by using a renewal bioassay method where the exposure medium was exchanged every 24h to maintain the toxicant strength and the dissolved oxygen level and to minimize the levels of ammonia excretion throughout the experiment. Water was aerated with an electric air pump during fish exposure.

Five fish from each replicate of both control and treatment groups were taken and sacrificed. Muscle, brain and gill were carefully removed. One gram of each organ was taken and crushed in 5 mL of deionized water with the help of mortar and pestle. The whole each crushed sample was taken in a glass tube using Teflon coated mechanical tissue grinder for homogenization at the speed of 1000 rpm for 10 min. The homogenates were then centrifuged at 4500 rpm for 30 min. The supernatants were stored at 0 to -5oC and then used for estimations of protein according to the Biuret method (Gornall et al., 1949). The values were presented as Means ± SD of three replicates. For ANOVA and level of significance determination, Excel and Origin 9were used.The Tukey HSD test was used to determine the significant difference within the treated groups.

Table I shows the protein contents in brain, gills and muscles of fish Oreochromis niloticus. A significant decrease in total protein content as compared to control was noted in all organs, total protein level was exceeded only in control 48h in brain (19.33±0.58) and muscle tissues (27.02±0.57). The significance decreased level ranged from P < 0.01 in brain to P < 0.00 in gill and muscle tissues. Thus, the order of toxicity recorded in the present study was chlorpyrifos>malathion> lambda-cyhalothrin.

The decline in serum total protein content was in fish Rhamdia quelen also reported by Borges et al. (2007). According to Das et al. (2004), reduction in serum total protein content was either due to the haemolysis of RBCs creating plasma dilution or protein catabolism where proteins convert to energy. Sastry et al. (1982) have also reported depletion of total protein content in the plasma of fish when exposed to curacron. Radha et al. (2005) reported decline in protein level due to demethoate. Reduction in serum total protein content was observed in Cyprinus carpio (Maruthanayagam and Sharmila, 2004) and in Clarias gariepinus (Yekeen and Fawole, 2011) when exposed to monochrotophos and endosulfan, respectively. Ogueji and Auta (2007) observed the profound effects of

Table I. Effect of pesticides on total protein (mg/mL) content of brain, gills and muscles of Oreochromis niloticus after 24 h and 48 h exposure.

Results are mean (X ± SD) of 3 observations shows the standard deviation values are significant at P < 0.001 when compared with control values; the values of control and pesticide treated groups are based on 24 h and 48 h. The same alphabet indicates that the mean values are not significantly different (P>0.05).

λ-cyhalothrin on serum total protein level in Clarias gariepinus. Similar findings indicated that protein is the major source of energy, there reduction resulted in high energy need increased under malathion stress in Cyprinus carpio (Malla-Reddy, 1987; Kale et al., 2006). Decreased trend in total protein level was also observed in Nile Tilapia (Oreochromis niloticus) when exposed to cypermethrin (Korkmaz et al.,2009). During stress condition in organisms proteins might be involved in the compensatory mechanism, when fish exposed to malathion (0.5 ppm) the protein level was decreased (Fahmy, 2012). Degradation in total protein level was also noted in fish response to deltamethrin (Ullah et al., 2019a). Hatami et al. (2019) reported a decrease in total protein level in fish when exposed to 25 and 50 mg/ L of chlorpyrifos as compared to control group. Ahmad et al. (2012) noted a decrease in total protein contents in zebra fish, Danio rerio (Hamilton) in response to λ-cyhalothrin. Mommsen and Walsh (1992) also suggested that fish can obtain energy during stress by the catabolism of protein. David et al. (2004) and Parthasarathy and Joseph (2011) also reported decreased] in protein levels in C. carpio and Oreochromis mossambicus in response to cypermethrin and λ- cyhalothrin, respectively.

The results of this study indicate that these pesticides (malathion, chlorpyrifos and λ-cyhalothrin) are extremely toxic to the fish Oreochromis niloticus and the total protein contents in the brain, gill and muscle tissues are decreased.

The laboratory facilities in the lab of Bahria University, Medical and Dental College provided by Assistant Professor Dr. Mehreen Lateef is gratefully acknowledged.

The study was ethically approved by the University of Karachi, Pakistan.

The authors have declared no conflict of interest.