ISBN: 978-83-60043-10-3 - eurobic9

Eurobic9, 2-6 September, 2008, Wrocław, Poland
P22. Accumulation and Biotransformation of Arsenic by Embryos of
Zebrafish (Danio rerio)
M.A. Bryszewska a , S. E. Hannam b , R. Munoz Olivas c , C. Camara c
a Technical University of Lodz, Faculty of Biotechnology and Food Sciences, Institute of General Food
Chemistry, ul. Stefanowskieg 4/10, 90-924 Lodz, Poland
e-mail: malbrysz@snack.p.lodz.pl
b University of Waterloo, Chemistry Department, 200 University Avenue West, Waterloo, Ontario, Canada
c Universidad Complutense Madrid, Facultad de Ciencias Quimicas, Dpto. Quimica Analitica, Madrid, Avda.
Complutense s/n, 28040 Madrid, Spain
Anthropogenic activities and natural sources cause that arsenic is ubiquitous element detected in low
concentrations in virtually all environmental media. Investigations performed over the last 25 years revealed a
large number of naturally occurring arsenic compounds. It is clear that arsenic metabolism is complex, moreover
it was demonstrated that pathways of biotransformation varies in the different organisms. Embryos of zebrafish
have consistently demonstrated their usefulness as a model organism for studies vertebrate development and
their responses to external stimulus, therefore are an ideal system to study the effects of arsenic exposure on its
accumulation levels and organisms ability of biotransformation the element. The aim of the present work was to
estimate arsenic accumulation by single embryos, to observe individual differences in the element accumulation
and trace element biotransformation. The ability to measure arsenic content in single embryos is important as it
allows for the determination of differences in uptake between each embryo within a group and between embryos
in different replicas. For the purposes of this work a method to directly introduce whole single embryos into the
graphite furnace (ETAAS) was elaborated. The significant matrix effects due to complexity of the sample were
overcome by the use of a palladium modifier (0.8 g L -1 ) and hydrogen peroxide (12 %) as an oxidizing agent to
aid in the decomposition of the sample. The results obtained from this direct method of total arsenic
measurement were in agreement with those from more common sample preparation methods of acid and
ultrasonic digestion when measured using ETAAS and ICP-MS. Arsenic content was measured for embryos that
were exposed to the solution containing AsO3 3- or AsO4 3- in the concentrations of 1 mg L -1 and 0, 05 mg L -1 .
Measurement of total arsenic content in the single embryos showed that there is a large variability in arsenic
content between single individuals
- embryos of age 24hpf (hour post fertilisation): control group: 0.027÷0.046 ngAs/embryo (RSD 17, 94),
enriched group 0.045÷0.110 ngAs/embryo (RSD 26, 51);
- embryos of age 48hpf: control group: 0.042÷0.079 ngAs/embryo (RSD 21, 69), enriched group
0.068÷0.202 ngAs/embryo (RSD 32, 94).
This is likely caused by biological factors that differ between embryos which may have an impact on As uptake
and its accumulation. Arsenic speciation analysis performed using HPLC ICP MS, revealed that the zebrafish
embryos exposed to 1 mg AsO4 3- L -1 were able to reduce arsenate to arsenite. Relation of pentavalent form to the
trivalent form was decreasing during the time reaching 75% of AsO3 3- and 25% of AsO4 3- of detected in the
extracts arsenic, at the age of 120 hpf. Lack of the other forms like methylated form is suprising. It is well
documented and observed for the different kinds of the organisms that reduction As V is a initial stage on the
metabolitical path leading to the methylated form like monomethylarsenic acid or dimethylarsenic acid.
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