BIOACCUMULATION AND METABOLISM OF ARSENIC BY RAINBOW TROUT, SALMO GAIRDNERI

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Date
1980-07
Authors
OLADIMEJI, ADEBAYO A.
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Abstract
Uptake of inorganic arsenic from water and food and i t s retention by rainbow t r o u t , Salmo gairdneri, were determined using radioactive tracer methods. Arsenic taken up from both vectors was accumulated into two compartments which ware distinguishable by differences in their fractional clearance rates. The uptake rates of arsenic from water, though low were d i r e c t l y related to the concentrations of arsenic in water. However, arsenic accumulation from food was more e f f i c i e n t , with a minimum assimilation of 50% of ingested dose. Clearance of arsenic was in two phases following uptake from both water and food. The fast compartment, which comprised from 19-30% of the dose had a h a l f - l i f e of less than 1 day. The slow-clearing compartment had a h a l f - l i f e of 4.3-5.0 arjd 6.4 days following uptake from water and food respectively. There was no effect of route of exposure on the relative size of the fast and slow-cllearing compartments. The results on the routes of arsenic elimination by rainbow trout demonstrate that fecal and g i l l routes can be of equal magnitude and could account for 80% of total arsejnic loss, urinary excretion accounting for 20% or less. Urine, unlike in mammals, seems to play a minor role in the elimination of arsenic by rainbow trout. Chemical speciation of arsenic was examined by radiotracer and chromatographic techniques applied to muscle, l i v e r , g i l l , kidney, blood, b i l e and urine of trout following an oral dose of 74AS as arsenic acid. The r a t i o of total organic to inorganic arsenic increased rapidly with time in a l l tissues, with the organic fraction accounting for about 50% at 6 h postdose and over 80% at 24 h. An organoarsenic metabolite was shown by t h in layer chromatography (TLC) to have the same Rf value as ethylarsenobetaine and, this compound accounted for t i e major portion of the total arsenic in a l l tissues as well as urine and b i l e sampled 24-96 h postdose. The effect of acclimation to sublethal dose of arsenic on whole body clearance rates, tissue d i s t r i b u t i o n and binding of a subsequent dose of 74As was examined. Whole body clearance of 74 As was twice as fast in preexposed f i s h . The l i v e r and b i le of preexposed f i s h contained higher concentrations of arsenic than those for the control. Gel chromatography of liver cytosol proteins revealed no differences in arsenic-protein binding pattern in control and preexposed f i s h . Arsenic elution was in two peaks, the f i r s t peak bound to proteins of molecular size 19,000 daltons and the other corresponding to moleculer size 3,000 daltons. Trout exposed to arsenic levels of 20 mg As kg-1 diet for a duration of 2 to 8 weeks showed reduced growth Compared to the control. The l i v e r contained the highest level of arsenic among the tissues analysed.
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A Dissertation submitted to the School of Graduate Studies of the University of Ottawa in partial fulfillment of the requirements for the degree of Doctor of Philosophy Department of Biology University of Ottawa Ottawa, Ontario
Keywords
BIOACCUMULATION,, METABOLISM,, ARSENIC,, RAINBOW,, TROUT,, SALMO GAIRDNERI
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