Bisphenol A is a commercially used chemical, an additive in the production of polycarbonate plastics as a developing agent in the manufacturing of thermal paper and epoxy resins. Bisphenol A is also present in dental sealants, water bottles, and baby bottles, paper coatings, adhesives, flame retardants, food, and beverage packaging (Staples et al., 1998). Bisphenol A is one of the highest volume chemicals produced worldwide and its demand is increasing due to the ever-increasing demand and production of plastic products. Since aquatic environments are the ultimate sink of all anthropogenic chemicals, aquatic animals including fish are often exposed to these chemical compounds (Routledge et al., 1998, Metzler and Erica, 2001). In the present study, Absolute organ weight increased and relative organ weight of all of the visceral organs (Gills, Liver, and kidney (Table: 1, 2) except the brain decreased in fish. Many reports on the relative organ weight of different vertebrates exposed to different toxicants are available in previous studies but scanty of information available about bisphenol A effect on absolute and relative organ weight of freshwater fish. In previous research work, similar results showed like decrease in the relative weight of visceral organs (liver, kidneys) was observed in fish (Gaffar et al., 2019; Hussain et al., 2019) rats (Rattus norvegicus) (Rubin et al.,2019; Cervantes-Camacho et al., 2020) exposed to different toxicants. Hematological parameters of blood are considering the greatest indicator of physiological stress in the various aquatic and terrestrial organisms (Ghaffar et al., 2017a). In the present study, decreased hemoglobin concentration, lymphocytes, monocytes, and pack cell volume in fish exposed to bisphenol A has been reported. Parameter values are lowered due to the rapid oxidation of hemoglobin, hemolysis, and destruction of erythrocytes (Ghaffar et al. 2016; Gul et al. 2017). RBCs reduction, increased WBCs and neutrophils also observed in present work at higher concentrations of bisphenol A. An increase in neutrophils count could be due to immunological reactions expressive to injury in tissues of exposed big head carp. While in previous reports, similar results like RBCs reduction decreased in Hb, MCHC, and increase in WBCs and neutrophils were studied in common carp (Ghaffar et al., 2018), African catfish (Nashwa, 2014; Sisodiya et al., 2018) Labeo rohita (Krishnapriya et al., 2017) and Clarias gariepinus (Pathania et al., 2019) exposed to sublethal concentrations of bisphenol A. Hematological abnormalities may be due to erythrocyte destruction in blood-forming cells, increase the production of free radicles, and poor supply of oxygen through gills. Moreover, many reports of hematological parameters are also available on other vertebrates like the Albino mouse (Moselhy, 2015), Rats (Karnam et al., 2015) Yellowfin seabream (Yaghoobi., 2017), and adult cockerels (Hussain et al., 2019) exposed to toxicants. In the present research work, tissue damage observed in bighead carp caused by a higher concentration of BPA. Damage may occur due to stress conditions which induced the inflammatory response of fish tissues led to overproduction of white blood cells. Serum biochemistry analysis gives a clear indicator of pollutant exposure which is a mirror image of environmental contamination, which is useful for tissue pathophysiological status identification (Sayed and Hamed 2017; Abdel-Tawwab and Hamed, 2018). Furthermore, it has been reported that bisphenol A induces adverse effects on serum biochemical index in adult fish, leading to a defect in growth performance and fish health (Wang et al. 2016). In the present study, serum biochemical parameters like ALT, AST, and ALP increased significantly in treated fish in association to stress induced by bisphenol A. Serum biochemical parameters like serum albumin quantity and serum total protein decreased in the present investigation. However, increased glucose, cholesterol, and lactate dehydrogenase level were observed due to stress conditions in treated fish. Serum creatinine and uric acid are essential factors for muscle and purine metabolism for renal safety and kidney function (Hamed and Tawwab, 2017). Urea and creatinine levels were also increased in the liver and kidney which indicated that disturbance in filtration mechanisms and damages of kidneys and liver tissues of fish exposed to bisphenol A in the current experiment. Many previous reports are also available in other species exposed to bisphenol A. Previously, abnormal liver, kidney enzymes, an increase in hepatic enzymes as ALT, ALP, AST, abnormal urea ad creatinine, fatty liver disease, edema, vacuolation of hepatocytes, abnormal structure of cells, degeneration of structural protein due to increase in hepatic enzymes were observed in O. niloticus (Abdul-Tawwab and Hamed, 2018), Zebrafish (Renaud et al., 2017; Ngo et al., 2017 ), C. catla (Faheem et al., 2019), C. gariepinus (Makinwa & Uadia, 2017) H. fossilis (Pal & Reddy, 2018) due to exposure of bisphenol A. Moreover, in literature, many reports of serum biochemistry are present on other species like rats (Pal et al., 2017; Geetharathan & Josthna, 2016).
In the current study, histopathological responses of the fish indicate the degree of damage caused by BPA to the liver of fiah (A.nobilis). In this present research work, histopathological lesions in liver tissues of fish were congestion, decreased cytoplasmic space, vacuolar degeneration, increased sinusoidal space, karyolysis of hepatocytes, and necrosis exposed to the higher concentration of BPA. Similar results are available in previous other species of aquatic organisms like ruptured central vein, lipids like vacuolization, macrophage, and lymphocytes infiltration, ruptured and degenerated hepatocytes in Ctenopharyngodon Idella (Faheem et al., 2017), seabream (Carnevali et al., 2017) exposed to sublethal concentration of BPA. The current study suggests that bisphenol-A is capable of causing damage to vital organs (brain, gills, lungs, and liver) of fish at biologically appropriate concentrations, contributing to altered rates of enzymes that could potentially affect fish health and reproduction. If these fish with high BPA load are routinely eaten by humans may also cause similar health problems. In the current study, kidneys of bisphenol A treated fish also showed microscopic lesions as edema, ceroid formation, glomerular degeneration, Bowman’s space, congestion atrophy of tubules, and atrophy of lumen of renal tubules. However, similar results as necrosis, vacuolation, aggregation of melanomacrophages, degeneration, blood congestion, cellular rupture, nuclear hypertrophy degeneration, pyknotic nucleus, and reduction of lumen were observed in other species of fish like Heteropneustes fossilis (Pal & Reddy, 2018), tilapia (Vasu et al., 2019), Catla Catla (Faheem et al., 2017) exposed to BPA has been reported in previous studies. Like previous studies, bisphenol A is responsible for kidney damage in bighead carp in current research because kidneys are primary organs to be infected by any type of pollutant (chemical, insecticide, pesticide, etc) in water bodies (Hussain et al., 2017). The degree of the damage caused and the degenerative changes that have occurred in the brain of the fish due to BPA toxicity have been progressive over the exposure, indicate that the histopathological responses depend not only on the concentration of chemicals but also on the duration of the fish exposure time to this toxicant. Several authors have recorded various histopathological changes in fish brains after exposure to different chemical substances (Ayoola & Ajani, 2008; Lakshmaiah, 2017; Ding et al., 2018; Murali et al., 2018; Gobi et al., 2018). Scanty of the latest information available on histopathological differences in brain tissues of fish exposed to bisphenol-A. However, few reports are present in our assessed data on histopathological changes of the brain of fish like C. gariepinus (Ayoola et al., 2008), L. rohita (Das et al., 2000), O. punctatus (Pugazhvendan et al., 2009), C. carassius (Mattsson et al., 2017), C.catla (Bose et al., 2013), O. niloticus (Ayoola et al., 2008; Ding et al., 2018), O. mossambicus (Gobi et al., 2018; Murali et al.,2018), C. carpio (Lakshmaiah, 2017) exposed to toxicants.
Literature exhibited that histopathological lesion formation in the gills of fish is a suitable tool to screen the effect of different contaminants in the freshwater ecosystem. It is because the gills are facing direct contact with water pollutants and gills are the 1st organ in which contaminants enter. Gills are those important organs that act as a medium for gaseous exchange, boundary between water and fish, ionic compounds balancer, and are responsible for osmoregulation mechanism (Gaffar et al., 2018). In the present study, histopathological lesions in the gills of fish include lamellar fusion atrophied lamellae, uplifting of lamellae, congestion, and disorganization of primary, secondary lamellae. Likewise, results as Necrosis, lamellar deformation, loss of epithelium, vacuolations, hyperplasia, tubular alteration, neoplasia, hemocyte infiltration, hypertrophy, pyknosis, and histological aberrations were observed in other organisms like Van fish (Oguz et al., 2018) and C. fluminea, (Benjamin et al., 2019) exposed to different concentration of BPA. In current research work edema, neutrophilic myocarditis, hemorrhages and deposition of fibrin were observed in heart of big head carp exposed to different concentrations of bisphenol A. In one of the previous reports, calcific aortic valve disease (CAVD), including extra-cellular matrix (ECM) alteration were confirmed by histopathology for high-level of BPA exposure, and structural defects (abnormal curvature) of the atrio-ventricular valves corresponded with impaired cardiovascular function (reduced ventricular beat rate and blood flow) were observed in zebra fish (Brown et al 2019) exposed to bisphenol A. Few reports are available on histological changes of heart in fish exposed to bisphenol A. However, many reports of heart histology are available on rats. Potential Toxic Effect of Bisphenol A on rats (Bahey et al., 2019, Amin, 2019, Eweda et al 2020, Rasdi et al., 2020) as myocardium in the form of disarrangement of myofibers, hypertrophy of myocytes, myocardial fibrosis, and dilatation of intramyocardial arterioles were observed in previous rsearch work. In the present study histopathological changes in intestine are extensive vacuolation of enterocytes, inflammatory response, congestion, necrosis and sporadic hemorrhages in fish exposed to different concentrations of bisphenol A. like heart and brain scanty of information about BPA effect on intestine of fish is available in my assessed reports. Previously, histological Intestinal alterations in fish Dicentrarchus labrix (peda et al., 2016) was reportd. Similarly, histopathological alteration in intestine of fish Lates niloticus (Ibrahim et al 2014), Sparus aurata (Rathee and Radha, 2015), H.fossilis (Pradip et al., 2019) were exposed to toxicants have been reported. The fish under toxicant stress started the utilization of immediate sources of energy like protein, lipid, and carbohydrate, resultantly depleting the levels of these nutritive sources in the muscles as these all are interrelated in metabolism during the citric acid cycle ( Sulekha and Marcy, 2011; Muralidharan, 2014. In the present study, protein contents depletion in the fish muscle might be because of the diversion of energy due to the toxic stress of bisphenol A (Sweilum, 2006; Sobha et al., 2007; Sulekha and Marcy, 2011; Karmai et al., 2016). The decrease in protein in the meat of fish could be due to a reduction in salt and water-soluble (Chomnawang et al., 2007) or because of autolytic degradation combine with endogenous enzymes and bacteria (Hultmann and Rsted, 2004). The decrease in protein content was probably due to the leaching of soluble components especially water proteins (Osibona and Ezekiel, 2014; Ihanacho et al., 2017). Scanty of work available on body composition on freshwater fish exposed to BPA In the present study lipid contents of fish decreased at a higher concentration of bisphenol A. Previously, similar reports available on C. gariepinus (Mahboob et al., 2018), Tilapia (Sana et al., 2017) exposed to toxicants. Presently moisture contents were also decreased like protein and lipid contents in fish exposed to bisphenol-A. However, increased moisture content was observed in C.catla, L. rohita, and C. mrigala (Ghazala et al., 2018). In the present study, Ash content increased after exposure of fish to high concentrations of bisphenol A. Similar results available previously, (Rao et al., 2010; Hussain et al., 2019). Limited information is available in the literature about an effect of industrial effluents on the proximate composition and amino acid profile of freshwater fishes and their use as a biomarker of toxicant contamination (Hussain et al., 2019). The findings of this research work have indicated that industrial contaminant (bisphenol A) probably had adversely affected the proximate composition of fish meat in A.nobilis. hence, more research work is required to verify these findings.