Alterations in protein metabolism in selected tissues of fish, Cyprinus carpio, during sublethal concentration of cypermethrin

Mortality, oxidative stress and hepatotoxicity in juvenile African catfish, Clarias gariepinus Burchell, exposed to lead and cypermethrin

In this study, juvenile catfish (Clarias gariepinus) were exposed to 2 mg/L Pb, 0.5 μg/L cypermethrin, or both for 96 h. Survival ranged from 100% in both treatments without cypermethrin, to 50% in fish exposed to cypermethrin only or the mixture. There were significant decreases in liver lysozyme, γ-glutamyl transpeptidase, and alanine aminotransferase activities in fish exposed to cypermethrin or the mixture. Liver aspartate aminotransferase activity (AST) showed a significant reduction after exposure to Pb or cypermethrin alone, and the effect of the mixture on AST was additive or potentially synergistic. Liver lipid peroxidation (LPO) was increased in fish exposed to the mixture compared to those exposed to cypermethrin only, indicating that Pb presence enhanced LPO caused by cypermethrin. Our study demonstrates the potential for toxic interaction between Pb and cypermethrin in fish and suggests that due to the varying responses to contaminant mixtures in our study, researchers should consider using a variety of biomarkers.

Modulation in the protein metabolism by subacute sodium cyanide intoxication in the freshwater fish, Labeo rohita (Hamilton)

The effects of exposure to one-third and one-fifth sublethal concentrations (0.106 and 0.064 mg/L) of sodium cyanide on protein metabolism on freshwater carp, Labeo rohita, was studied. Three functionally different tissues, namely, the liver, muscle, and gills, were studied after 5, 10, and 15 days. Exposures produced marked changes in protein metabolic profile in all tissues studied. These changes were more pronounced in the one-third sublethal concentration, suggesting a cumulative action of toxicant. This investigation revealed that the total, structural, and soluble proteins and urea content in all the three tissues were decreased, whereas free amino acids, ammonia, and enzyme activity (i.e., protease, alanine aminotransferase, and aspartate aminotransferase) exhibited elevated levels at both sublethal concentrations. Variation in protein metabolism in the fish, induced by sodium cyanide, demonstrated its toxic effects on cellular metabolism, thereby leading to impaired protein synthetic machinery. The results of the present study indicate that a mechanism of impaired energy transformation has direct action on the fish, L. rohita, and its impact is clearly evident from the change in the nutritional content of the fish.

Cypermethrin induced alterations in nitrogen metabolism in freshwater fishes

In the present study, two fresh water fishes namely, Channa punctatus and Clarias batrachus, were exposed to three sub-acute concentrations of synthetic pyrethroid, cypermethrin, for 96 h to evaluate the role of amino acids in fulfilling the immediate energy needs of fishes under pyrethroid induced stress as well as to find out the mechanism of ammonia detoxification. The experiments were designed to estimate the levels of free amino acid, urea, ammonia and the activities of aspartate aminotransferase (AAT), alanine aminotransferase (AlAT), glutamate dehydrogenase (GDH), glutamine synthetase (GS) and arginase in some of the vital organs like brain, gills, liver, kidney and muscle of both fish species. The significant decrease in the levels of amino acids concomitant with remarkable increase in the activities of AAT, AlAT and GDH in these vital tissues of fish species elucidated the amino acid catabolism as one of the main mechanism of meeting out the immediate energy demand of the fishes in condition of cypermethrin exposure. The levels of ammonia were significantly increased at 10% of 96 h LC(50) of cypermethrin in the different organs such as brain, gills, liver, kidney and muscle of both fish species while 15% and 20% concentrations of 96 h LC(50) of cypermehrin registered remarkable decline in both fish species. The differential increment in the activities of GDH, GS and arginase and in the level of urea established three different alternative mechanisms of ammonia detoxification. The results indicated that in C. punctatus, the prevalent mode of nitrogen excretion is in the form of conversion of ammonia into glutamine and glutamate while in C. batrachus, the excessive nitrogen is excreted in the form of urea synthesized from ammonia.

Effects of water pollution in Lake Mariut on gonadal free amino acid compositions in Oreochromis niloticus fish

In the present report, we have determined the gonadal free amino acid compositions in Oreochromis niloticus collected from three sites in Lake Mariut: SE basin (less polluted), main basin (moderately polluted) and SW basin (highly polluted), in an attempt to develop sensitive biomarker to evaluate pollution effects from multiple sources. Variations of free amino acids (FAAs) were apparent in the polluted sites; total FAAs in testes and ovaries exhibited significant increases as compared to the less polluted site. This increase was attributed to increases in all individual amino acids including essential and non-essential ones. ANOVA indicated significant changes in all testicular FAAs, excluding phenylalanine. Levels of non-essential amino acids showed obvious alterations in ovaries. However, the increase in most essential amino acids, although insignificant, yet it was quite observable. In addition, the ratio of essential to non-essential amino acids was insignificantly decreased in gonads. This may be indicative of changes in protein metabolism.

Alterations in carbohydrates and the protein metabolism of the harmful freshwater vector snail Lymnaea acuminata induced by the Euphorbia tirucalli latex extract

To know the short- as well as long-term effect of aqueous latex extracts of Euphorbia tirucalli on carbohydrate and protein metabolism, the snail Lymnaea acuminata was exposed to sublethal doses of 0.37 and 0.55 mg/L for a 24-h and 0.20 and 0.31 mg/L for a 96-h exposure period. Significant (P<0.05) alterations in the glycogen, pyruvate, lactate, total protein, and free amino acid level, as well as in the activity of enzyme lactic dehydrogenase, succinic dehydrogenase, cytochrome oxidase, protease, aspartate aminotransaminase, and alanine aminotransaminase were observed in the nervous, hepatopancreatic, and ovotestis tissues of the freshwater vector snail L. acuminata exposed to sublethal doses of E. tirucalli latex extract. The alterations in all biochemical parameters were significantly (P<0.05) time and dose dependent. After the 7th day of the withdrawal of treatment, there was significant (P<0.05) recovery in glycogen, pyruvate, lactate, total protein, and the free amino acid level and in the activity of the lactic dehydrogenase, succinic dehydrogenase, cytochrome oxidase, protease, aspartate aminotransaminase and alanine aminotransaminase enzymes in all three of the studied tissues of the snail, which supports the view that the plant product is safe for use as a molluscicide for the control of harmful freshwater vector snails in the aquatic environment.

Protein synthesis costs could account for the tissue-specific effects of sub-lethal copper on protein synthesis in rainbow trout (Oncorhynchus mykiss)

This study investigates protein synthesis, following exposure to sub-lethal Cu, in rainbow trout in vivo and in vitro. The investigation has two aims: to determine if perturbations in protein synthesis, compared with other physiological changes, are a biomarker of Cu pollution and to evaluate the most productive role of cellular models in ecotoxicology. Protein synthesis rates were measured by labelling with 3H-phenylalanine. In vivo this was applied by a single (i.p.) injection and in vitro by bathing the cells in 3H-phenylalanine labelled culture media. The effects in vivo were tissue specific. After 3 weeks' exposure to 0.7 microM Cu only skin protein synthesis was reduced. Gills and liver from the same fish were unaffected. This reduction in skin protein synthesis appears to be more sensitive than some other biomarkers reported in the literature. However, Cu concentrations greater by orders of magnitude were required to reproduce this reduction in protein synthesis in skin cell explants (200 and 400 microM). Hepatocyte protein synthesis was unaffected by 10, 20 and 40 microM Cu and a separate investigation has also shown that 25 and 75 microM Cu does not effect protein synthesis in cultured gill cells. Oxygen consumption rates were also measured in vitro by monitoring the decline in O2 partial pressure. The Cu concentrations given above resulted in a decline in O2 consumption rates in the respective cell types. By measuring protein synthesis and O2 consumption after treatment with a protein synthesis inhibitor (cycloheximide), the costs of protein synthesis were also determined. Synthesis costs in hepatocytes are close to the theoretical minimum and are only marginally affected by Cu. Gill cell synthesis costs are also minimal and are unaffected. In skin explants, the reduction in protein synthesis was accompanied by greatly increased synthesis costs. This in vitro result offers a hypothesis as to the tissue-specific effects in vivo; i.e. the energetic demand of protein synthesis may determine tissue sensitivity or susceptibility. Cell or tissue types with high protein synthesis rates are able to avoid detrimental increases in the synthesis cost when exposed to Cu. In tissues with a low protein synthesis rate any further reduction is more likely to incur a potentially damaging increase in protein synthesis costs. Thus, whilst in vitro models may have little practical use in environmental monitoring, they may be best used as a mechanistic tool in understanding susceptibility or tolerance to sub-lethal Cu.