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Summary
High levels of
POPs have been found in glaucous gulls from the Barents Sea area. Tissue contaminant
levels are the result of both exposure via the food and metabolism by specialized enzymes
(monooxygenases) in the liver. Often, contaminant metabolism is classified into phase I
and phase II reactions, and hepatic phase I and phase II enzymes play an important role in
contaminant metabolism. Previous investigations have shown that hepatic EROD-activity
(phase I enzymes) is low in liver from glaucous gulls and only marginally associated with
PCB-loads. However, the absence/low levels of certain congeners indicates that at least
some congeners are metabolised and excreted. This metabolism may be a result of phase II
enzyme activity. It is therefore nessesary to investigate the presence and activity of
both phase I and phase II enzymes in glaucous gulls in order to assess the total metabolic
capacity in this species. During a field expedition to Longearbyen in September 1998 liver
samples from 16 glaucous gulls were collected. These samples will be analysed for phase I
and phase II enzyme activity. Information about levels of persistent organisc contaminants
in the same individuals will be obtained from The Norwegian Polar Institute. The results
may provide valuable information on the subject of biomarkers for use in future monitoring
programmes.
This project will be
closely integrated with the other projects on glaucous gulls financed by the effect
programme.
Scientific Background
The Svalbard
area is a key site for seabirds. The total breeding population of glaucous gull (Larus
hyperboreus) on Svalbard has roughly been estimated to 1 000 - 10 000 pairs (Mehlum
and Bakken, 1994). In the Svalbard area a considerable number of dead glaucous gulls, with
high levels of PCBs have been found (Gabrielsen et al., 1995). No cause of death
has been found, but it has been indicated that the contamination levels may be an
important problem lowering survival and possibly also reproduction in some areas (Isaksen
and Bakken, 1995).
The glaucous gull is
the most important avian predator in the Arctic ecosystem and due to its high trophic
levels, it is particularly vulnerable towards contaminant exposure. The mobilization of
body fat reserves during periods of food limitation may result in the release of
accumulated lipophilic contaminants, and a temporary increase in blood contaminant levels
may occur (de Swart et al., 1995). The resulting acute exposure to high contaminant
levels imposes a higher risk upon these animals than indicated from tissue concentrations.
This fact gives rise to concern because many contaminants may have a detrimental effect on
the health and reproductive performance of animals.
Tissue contaminant
levels are the result of both exposure via the food and metabolism by specialized enzymes
(monooxygenases) in the liver. Concequently, the metabolic capacity of a species
determines contaminant accumulation patterns as well as total body burdens (Boon et al.,
1992; Bruhn et al., 1995). Often, contaminant metabolism is classified into phase I
and phase II reactions, and hepatic phase I and phase II enzymes play an important role in
contaminant metabolism.
The cytochrome P450
(CYP) enzyme system is considered as most important in the phase I metabolism. Important
phase II enzymes include UDP glucuronosyl transferases (UDPGT) and glutathione
S-transferases (GST). Both phase I and phase II enzymes may become more active as a result
of contaminant exposure and may as such be used as bioindicators. Although the important
function of CYP and phase II enzymes in contaminant metabolism and contaminant toxicity is
undisputed, these enzymes have received relatively little attention in fish-eating birds.
Knowledge of these enzymes is essential since their presence and activity determines the
potential biological effects of contaminant exposure.
Species differences
in phase I and phase II metabolism are well known, and to date no comprehensive study on
different phase I and phase II enzyme activities in relation to contaminant accumulation
patterns in glaucous gull has been performed. However, in a study on the phase I enzyme
activity in glaucous gulls with relatively high levels of PCB, Henriksen et al. (1998)
showed that hepatic EROD-activity was low and only marginally associated with PCB-levels.
It is possible that low metabolic capacities could result in the high bioaccumulation of
these compounds, as field studies have shown. However, the absence/low levels of certain
PCB-congeners indicates that at least some congeners are metabolised and excreted. This
metabolism may be a result of phase II enzyme activity. Comprehensive studies on both
phase I and phase II enzyme acivity in glaucous gull is therefore necessary to evaluate
the total metabolic capacities of this species, and to aquire a better understanding of
the fate and potential toxicity of environmental pollutants in Arctic seabirds.
Results from studies
on detoxification enzymes may add valuble information to the knowledge of biomarkes that
may be used as early warning signals in environmental monitoring.
Methods
Field sampling
Samples of glaucous
gull liver were collected during a field expedition to Longyearbyen (Spitsbergen) in
September 1998. During the field work livers from 16 glaucous gulls were sampled and
frozen on liquid nitrogen. The field work was performed in co-operation with the Norwegian
Polar Institute’s project on glaucous gull ("Effects of persistent organic
pollutants (POPs) on the immune response and retinoid- and thyroid hormone status of
glaucous gull"). If the results from this first field work gives valuable information
to the subject of monitoring strategies, a second field work, together with the Norwegian
Polar Institute and NTNU, is possible. However, the cost for this is not included in the
budget in the present application.
Analyses
The biochemical
analyses will be carried out in the Laboratory of Physical Chemistry of Biomembranes,
Moscow State University (MSU), which has national accreditation and has participated in
inter-calibrations with different laboratories in Finland, Spain and UK, and at the
University of Utrecht, the Netherlands (Akvaplan-niva personell).
The liver samples that were
collected in Longyearbyen will be analysed for phase I and phase II enzyme activity. The
following analyses will be performed:
Phase I:
- Western blotting
Akvaplan-niva/University of Utrecht
- EROD Akvaplan-niva/University of
Utrecht
- Testosterone hydroxylation
Akvaplan-niva/University of Utrecht
- ECOD Akvaplan-niva/Moscow State
University
- AHH Akvaplan-niva/Moscow State
University
Phase II:
- UDP-GT enzymes
Akvaplan-niva/Moscow State University
- GST-enzymes Akvaplan-niva/Moscow
State University
In addition, the Moscow State
University will perform some analyses on EROD and possibly som other phase I enzymes, as
an intercalibration routine between the two involved laboratories.
Work Schedule
Field work September 1998
Results phase I enzymes January 1999
Results phase II enzymes January
1999
Data treatment February 1999
Reporting Spring 1999 (dependent on
results from NPs glaucous gull project on levels of PCB and pesticides)
When the results are
available it is planned to have a workshop with participants from Akvaplan-niva, Moscow
State University, Norwegian Polar Institute and NTNU. This workshop is not included in the
budgets presented in the present project application, but will be financed through the
Norwegian Polar Institute’s glaucous gull project.
Participants
The scientific
team is composed of scientists from Norway and Russia who have been co-operating for
several years. Scientists involved in this proposal have a large amount of experience in
Arctic marine biology, ecotoxicology and analytical chemistry. The proposed project will
be an integrated component of the ecotoxicology program of the Polar Environmental Centre
(Tromsø). The different research aspects are an expansion of and complementary to the
work already taking place or being planned. The main partners are:
| Institution |
Participant |
Akvaplan-niva
Polar Environmental Centre
N-9296 Tromsø
Norway |
Dr. T. Savinova
Dr. J. Wolkers
Dr. V. Savinov
C. Sc. A. Evenset |
Moscow State
University
119899 Moscow
Russia |
Dr. S.Kotelevtsev
Dr. L. Stepanova |
Budget
Total: NOK 230 000,-. NOK 100
000,- is applied for from the Effects Programme, while the remainder will be covered by
Akvaplan-NIVA and Moscow State University.
Co-operation with other projects
The results from the enzyme analyses will be compared with the
results on levels of PCB and pesticides in the same individuals. Results on levels will be
available from the glaucous gull project of the Norwegian Polar Institute ("Effects
of persistent organic pollutants (POPs) on the immune response and retinoid- and thyroid
hormone status of glaucous gull"). As the detoxification enzymes may be involved in
the formation of metabolites with gentoxic and mutagenic effects, the results from the
enzyme analyses will be made available for NTNU’s project within the effect programme
on glaucous gulls ( "Gentoxic effects in glaucous gulls"). The co-operation
between the projects of Akvaplan-niva, the Norwegian Polar Institute and NTNU may give
rise to common publications addressing the issue of future monitoring
methods.
References
Boon, J.P., van Arnhem, E., Jansen, S.,
Kannan, N., Petrick, G., Schulz, D., Duinker, J.C.,
Bruhn, R.., Kannan, N., Petrick, G.,
Schultz-Bull, D.E., Duinker, J.C. 1995. CB pattern in the harbour porpoise:
Bioaccumulation, metabolism and evidence for cytochrome P450IIB activity. Chemosphere, 31:
3721-3732.
Gabrielsen, G.W., Skaare, J.U., Polder, A.
and Bakken, V. 1995. Chlorinated hydrocarbons in Glaucous Gull (Larus hyperboreus) at the
southern part of Svalbard. Sci. Tot. Environ. 160/161: 337-346.
Isaksen, K. and V.Bakken. 1995. Breeding
populations of seabirds in Svalbard. In: Seabird populations in the northern Barents Sea.
Source data for the impact assessment of the effect of oil drilling activity (Eds.
Isaaksen, K and V. Bakken). Norsk Polarinstitutte Meddelelser Nr 135, p.11-35.
Mehlum, F and V.Bakken. 1994. Seabirds in
Svalbard (Norway): status, recent changes and management. In: Seabirds on islands:
threats, case studies and action plans. Bird Life Conservation Series No 1 (Eds.
Nettleship, D.N., Burger, J. & Gochfeld, M.) : 155-171.
de Swart, R.L., Ross, P.S., Timmernan, H.H.,
Hjiman, W.C., de Ruiter, E.M., Liem, A.K.D., Brouwer, A., van Loyeren, A., Reijnders,
P.J.H., Vos, J.G., Osterhaus, D.M.E. 1995. Short term fasting does not aggravte
immunosuppression in harbour seal (Phoca vitulina) with high body burdens of
organochlorines. Chemosphere 31, 4289-4306.
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