Protective role of ascorbic acid in fishes exposed to organochlorine pollution

Background-free in-vivo Imaging of Vitamin C using Time-gateable Responsive Probe

Sensitive optical imaging of active biomolecules in the living organism requires both a molecular probe specifically responsive to the target and a high-contrast approach to remove the background interference from autofluorescence and light scatterings. Here, a responsive probe for ascorbic acid (vitamin C) has been developed by conjugating two nitroxide radicals with a long-lived luminescent europium complex. The nitroxide radical withholds the probe on its “off” state (barely luminescent), until the presence of vitamin C will switch on the probe by forming its hydroxylamine derivative. The probe showed a linear response to vitamin C concentration with a detection limit of 9.1 nM, two orders of magnitude lower than that achieved using electrochemical methods. Time-gated luminescence microscopy (TGLM) method has further enabled real-time, specific and background-free monitoring of cellular uptake or endogenous production of vitamin C, and mapping of vitamin C in living Daphnia magna. This work suggests a rational design of lanthanide complexes for background-free small animal imaging of biologically functional molecules.

Toxicity of the pyrethroid pesticide fenvalerate to freshwater catfish Clarias gariepinus: lethality, biochemical effects and role of dietary ascorbic acid

Static bioassays were made in the laboratory to determine lethal concentration of the pyrethroid pesticide fenvalerate [(RS)-alpha-cyano-3-phenoxybenzyl (RS)-2-(4-chlorophenyl)-3-methylbutyrate] for the freshwater catfish Clarias gariepinus and effects of sublethal concentrations of the pesticide on some biochemical parameters of the fish. For exposure periods of 24 to 96 h, LC(50) values of fenvalerate ranged from 5.83-4.76 micro g/L and 4.24-2.94 micro g/L, respectively for water and acetone soluble fenvalerate. Two sublethal concentrations of fenvalerate were used in the bioassays for biochemical parameters: 2.1 micro g/L for 24 h and 1.4 micro g/L for 96 h exposure, both concentrations representing 50% of LC(50) value of acetone soluble fenvalerate for the respective exposure period. Hepatosomatic index, liver glycogen, alkaline phosphatase of liver and ascorbic acid of blood, liver, and kidney decreased while haemoglobin (Hb) %, plasma glucose levels and acid phosphatase level of liver increased after 24 h exposure to 2.1 micro g/L fenvalerate. Longer exposure (96 h) to even a lower concentration (1.4 micro g/L) of fenvalerate resulted in reduction of all the parameters (except Hb %) tested as compared with control. Fish previously fed for 60 days with a diet supplemented by a high level of ascorbic acid (100 mg/100 g diet) could reverse most of the effects caused by 24 h exposure to 2.1 micro g/L fenvalerate. A lower level of ascorbic acid (50 mg/ 100 g diet) supplement could not influence these effects of fenvalerate. Even the higher dose of ascorbic acid supplementation (100 mg/100 g diet) could not relieve the stress parameters, except for Hb% and HSI, when the pesticide was applied at 1.4 micro g/L for a longer time period (96 h).

Effects of cypermethrin on some biochemical parameters and its amelioration through dietary supplementation of ascorbic acid in freshwater catfish Heteropneustes fossilis

Static bioassays were made to evaluate efficiency of dietary supplementation of ascorbic acid to counter stress exerted by the pyrethroid pesticide, cypermethrin on freshwater catfish Heteropneustes fossilis. Three levels, a control and two sub-lethal concentrations (0.3 and 0.5 microg L(-1)) of cypermethrin were tested. Stress on H. fossilis was evident from the rise of plasma glucose level and reduction in the level of liver glycogen after 4 h of cypermethrin treatment. Acid and alkaline phosphatase activities of liver and ascorbic acid level of blood, liver and kidney also decreased significantly in H. fossilis exposed to cypermethrin as compared with control. Fish previously fed for 60 d with a diet supplemented by high level of ascorbic acid (1.0 g kg(-1)) could significantly reverse these effects. Fish fed a low level of dietary ascorbic acid (0.5 g kg(-1)) failed to counter the stress of cypermethrin.

Ascorbic acid supplementation of diet for reduction of deltamethrin induced stress in freshwater catfish Clarias gariepinus

Static bioassays were made to evaluate efficiency of supplementation of ascorbic acid to remove stress of pyrethroid pesticide deltamethrin from freshwater catfish Clarias gariepinus. Clarias gariepinus exhibited several symptoms of stress when treated with deltamethrin (0.005 mg/l) for 24 h. Hepatosomatic index, liver glycogen, ascorbic acid of blood, liver, and kidney decreased while plasma glucose levels increased. Fish previously fed for 60 days with a diet supplemented by a high level of ascorbic acid (100 mg/100 g) could remove most of the stresses. Low levels of ascorbic acid supplement did not remove the stress. Dietary supplement of ascorbic acid at also appropriate level appeared to be a good way to counter toxicity of deltamethrin to the catfish.

Utilization of ascorbate-2-sulfate in fish

Although most vertebrate animals synthesize L-ascorbic acid (C1), some animal species lack the ability to produce L-gulonolactone oxidase and are thus dependent upon a dietary source of vitamin C. Fish are unique among this latter group in that they store a chemically stable form of vitamin C and appear to metabolize this compound differently from other vitamin C-requiring organisms. Ascorbate-2-sulfate (C2) contributes to total body stores of ascorbate, but the commonly used assays for ascorbate concentrations in tissues and body fluids do not generally measure C2. An HPLC assay distinguishes between and measures both C1 and C2. Modification of the less exact but commonly used DNPH method can provide adequate data to estimate total vitamers C, C1, and (by difference) C2. Since vitamin C is a required component of feed for salmonids, catfish, eels, shrimp and carp, use of C2 in feed formulation would provide a bioavailable form of ascorbate which is heat and water stable at pH 4-13.

Effects of phenolic compounds on in vivo blood parameters of a fish Notopterus notopterus

Effects of phenol (P), dinitrophenol (DNP), pentachlorophenol (PCP) and their three combinations, antagonistic [(PCP + DNP)/P], additive [(DNP + P)/PCP] and synergistic [(P + DNP)/PCP], at three subacute concentrations (1/10th, 1/15th and 1/20th fractions of 96 h LC50) were determined on several blood parameters after 30 days exposure taking Notopterus notopterus as a test fish. Generally, RBC, WBC and PCV were found to be increased while CT, ESR, Hb, MCH, MCHC and MCV were decreased. However, PCP showed dual effects in many cases. CT and MCV were decreased in PCP alone and in (DNP + P)/PCP combination, while increased in (P + DNP)/PCP combinations while decreased in PCP alone. Again RBC and MCV were decreased/increased in DNP alone. Significance of findings is that these haematological parameters can be used as scientifically most accurate are reliable laboratory diagnostic indices by fish breeders, administrators and scientists as to know the state of health of fish population and to make warning about deleterious effects of phenolic compounds so that appropriate measure may be taken by all concerned to protect a valuable source of human food.