Hepatobiliary and hematological effects of dietary disodium arsenate heptahydrate in juvenile rainbow trout (Oncorhynchus mykiss)

Arsenic bioaccumulation and biotransformation in aquatic organisms

Arsenic exists universally in freshwater and marine environments, threatening the survival of aquatic organisms and human health. To elucidate arsenic bioaccumulation and biotransformation processes in aquatic organisms, this review evaluates the dissolved uptake, dietary assimilation, biotransformation, and elimination of arsenic in aquatic organisms and discusses the major factors influencing these processes. Environmental factors such as phosphorus concentration, pH, salinity, and dissolved organic matter influence arsenic absorption from aquatic systems, whereas ingestion rate, gut passage time, and gut environment affect the assimilation of arsenic from foodstuffs. Arsenic bioaccumulation and biotransformation mechanisms differ depending on specific arsenic species and the involved aquatic organism. Although some enzymes engaged in arsenic biotransformation are known, deciphering the complicated synthesis and degradation pathway of arsenobetaine remains a challenge. The elimination of arsenic involves many processes, such as fecal excretion, renal elimination, molting, and reproductive processes. This review facilitates our understanding of the environmental behavior and biological fate of arsenic and contributes to regulation of the environmental risk posed by arsenic pollution.

Hematological, biochemical and ionoregulatory responses of Indian major carp Catla catla during chronic sublethal exposure to inorganic arsenic

In the present study the acute toxicity of arsenic trioxide in fingerlings of Catla catla an Indian major carp was evaluated with renewal bioassay method. The median lethal concentration of arsenic trioxide to the fish C. catla for 96 h was found to be 20.41 ppm (with 95% confidence limits). From this a non-lethal dose of (2.041 ppm; 1/10th of LC 50 96 value) was selected and fingerlings were exposed to 35 d and hematological, biochemical and ionoregulatory responses were studied at days 7, 14, 21, 28 and 35. Arsenic trioxide produced a significant increase in hemoglobin, hematocrit, WBC count, plasma GPT levels and reduction in RBC count, plasma sodium, chloride, potassium, glucose, protein, GOT, LDH levels as compared to the control group. Gill Na(+)/K(+)-ATPase activity was influenced by arsenic trioxide exposure. A biphasic response was noted in the value of MCH and MCV. However the MCHC level was not altered in arsenic trioxide treated fish throughout the study period. Results of the present investigation suggest that arsenic trioxide affects the hematological, biochemical and ionoregulatory parameters of fish and alterations of these parameters can be useful in environmental biomonitoring of arsenic contamination.

Arsenic accumulation in a freshwater fish living in a contaminated river of Corsica, France

The impact of arsenic (As) discharge related to a past mining activity in the Bravona River and its tributary, the Presa River, was investigated in an edible fish, the brown trout (Salmo trutta). Fish was sampled in four stations along a contamination gradient. Arsenic was measured in five organs type (operculum, gills, liver, muscle, and axial skeleton). Almost 70 years after the suspension of the mining activity, As levels in water remain high. The results indicated a strong As contamination in fish collected downstream from the mine. The operculum, liver, and gills showed the highest As concentrations whereas levels in muscle were lower. A strong positive correlation between As concentrations in water and in tissues was observed. Bioaccumulation occurred preferentially in the gills, operculum, and liver. Since As levels in tissues of S. trutta followed the pollution gradient, this species appears useful as biomonitor for metalloid accumulation.

Gastrointestinal uptake of cadmium and zinc by a marine teleost Acanthopagrus schlegeli

Gastrointestinal metal uptake represents a potential route for metal bioaccumulation in marine fish. Drinking of seawater for osmoregulation causes constant waterborne exposure of the gastrointestinal tract. Tissue specific Cd and Zn accumulation and distribution were investigated in juvenile black sea bream (Acanthopagrus schlegeli) exposed to waterborne Cd (5.7 nM) and Zn (2.6 nM) for 4 h-7 days. The intestine accumulated a large portion of the Cd (43-58%) and Zn (18-28%), and had the highest Cd (>1.0 nmol g(-1)) and Zn (>1.8 nmol g(-1)) concentrations of all body fractions, suggesting that the intestines were the major uptake sites for these waterborne metals. Among all the segments of the gastrointestinal tract, the anterior intestine played the most important role in Cd and Zn uptake. A gastrointestinal injection assay was conducted to distinguish waterborne metal uptake by the intestines and the gills. The intestine contained over 90% of the Cd in the body after depuration for 3-7 days, suggesting that little waterborne Cd entered the rest of the body through the intestine, and that Cd may exert its toxic effects on the gastrointestinal system. In contrast, intestine retained less than 20% of the total Zn after depuration, suggesting that Zn tended to be transported from the intestine to the internal tissues via the cardiovascular system. The uptake kinetics of waterborne Cd and Zn by the intestines and the gills were determined as a first-order and saturated pattern, respectively, over a wide range of ambient metal concentrations (6.2 nM-4.5 microM for Cd, and 13 nM-15 microM for Zn). An in vitro intestinal perfusion assay investigated the effects of intestinal metal composition and drinking rate on uptake. The presence of EDTA significantly reduced intestinal Zn uptake to 11%, while cysteine improved it by 59%. The intestinal Cd and Zn uptake rates were unaffected by the perfusion rate.

The accumulation, distribution, and toxicological effects of dietary arsenic exposure in lake whitefish (Coregonus clupeaformis) and lake trout (Salvelinus namaycush)

A 20-day experiment was conducted to compare the accumulation, distribution, and toxicological effects of dietary As, as arsenate, in lake whitefish (LWF, Coregonus clupeaformis) and lake trout (LT, Salvelinus namaycush). Results of this experiment were used to design an experiment of longer duration in which one of the fish species was selected and exposed three times per week to lower dietary As doses. In the present study each treatment group was exposed to a combination of one of three doses of As (0, 100, or 1000 microg As/g) and one of two types of diet, no brine shrimp (NS) or with brine shrimp (WS) for a total of eight dosing events. Brine shrimp were added to determine whether their presence enhanced consumption of As-contaminated food. Modified feeding behavior occurred in both fish species fed As contaminated diets, with the exception of the 100 microg As/g NS food. Brine shrimp addition did not affect feed consumption of the As contaminated diets. Significant As accumulation occurred in stomach, pyloric caeca, intestine, liver, kidney, and gallbladder, but not in bile or muscle. As exposure did not have a significant effect on hepatic and renal metallothionein concentrations. Concentrations of lipid peroxides were only significantly elevated in the plasma of LT fed the 1000 microg As/g WS food. Liver somatic indices decreased significantly in both species, whereas hematological parameters were not affected in either species. Histological lesions occurred in gallbladder, liver, kidney, pyloric caeca and intestine from LWF. These lesions were not observed in LT; however, gallbladders were not examined in this species. Weight gain was lower in both species fed As contaminated diets, however, condition factors were not affected.

Investigations of the gallbladder pathology associated with dietary exposure to disodium arsenate heptahydrate in juvenile rainbow trout (Oncorhynchus mykiss)

Juvenile rainbow trout were fed semi-purified diets with (58 micrograms As/g diet) or without arsenic, added as disodium arsenate heptahydrate (DSA), under standard laboratory conditions for up to 12 weeks, to determine the time-course of development of gallbladder pathology in response to dietary DSA exposure, to correlate this pathology with levels of total arsenic and specific arsenic metabolites in the hepatobiliary system and thereby to attempt to gain some insight regarding the mechanism(s) by which the pathological changes develop. Gallbladder lesions associated with this level of dietary arsenic exposure to juvenile rainbow trout include acute inflammation with oedema of the submucosal tissues and sloughing of the epithelium within the first day of exposure, developing to chronic inflammation with fibrosis of the gallbladder wall. These changes may result from the toxic influence of arsenite absorbed into the epithelial cells. The arsenic content of washed gallbladder tissue is a sensitive indicator of recent dietary DSA exposure, while the chronic inflammatory lesion with extensive fibrosis of the gallbladder wall may provide a longer-term indicator of exposure to toxic levels of DSA in the diet of rainbow trout.