BIOACCUMULATION AND METABOLISM OF ARSENIC BY RAINBOW TROUT, SALMO GAIRDNERI
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.
Description
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