Please use this identifier to cite or link to this item: https://www.um.edu.mt/library/oar/handle/123456789/64547
Title: Effects of some pollutants on the hepatic cytochrome P450 dependent monooxygenases in fish
Authors: Cassar, Geraldine G.
Keywords: Animals -- Malta
Pollution -- Malta
Fishes -- Malta
Ecology -- Malta
Issue Date: 1994
Citation: Cassar, G. G. (1994). Effects of some pollutants on the hepatic cytochrome P450 dependent monooxygenases in fish (Master's dissertation).
Abstract: Cytochrome P450 dependent mixed function oxygenases are amongst the phase I enzymes which are very important in biotransformation. In the last two decades a number of field studies have demonstrated a positive correlation between the degree of induction of cytochrome P450 dependent mixed function oxygenases and the levels of polyaromatic hydrocarbons (P AHs) or polychlorobiphenyls in the environment or in the fish tissues. This has led to the use of mixed function oxidases as a biomarker of exposure to pollutants. Several factors influence this system and these have been reviewed in the present work. In the present study, the possible use of hepatic EROD induction in Serranus scriba as a biomonitoring tool of coastal contamination by P AHs was investigated. This species exhibited a high response factor and limited seasonal fluctuations in EROD activity. Furthermore this species is a simultaneous hermaphrodite (Havelange and Voss, 1993), thus eliminating any sex-linked variations in EROD activity, usually observed in other fish species. Moreover, induction in EROD activity in S. scriba sampled along the sewage plume at Wied Ghammieq - a known pollution gradient was demonstrated. All these demonstrate the feasibility of using this species as a biomarker of pollution. The results on the hepatic induction potential in S. scriba presented in this study are of general toxicological interest and will find application in the design of a biomonitoring programme for the Maltese coastal waters. Tributyltin (TBT) levels in local coastal waters have been reported to be significantly high in certain areas due to its use as an antifouling paint on ships and small watercraft (Axiak 1994). In the present study, the possibility that TBT contamination may interfere with the use of hepatic EROD induction in fish to biomonitor PAH pollution in ports and marinas was also investigated. Immature seabream, Sparus aurata were injected intraperitoneally either with different TBT doses in order to investigate the effect of TBT on the constitutive cytochrome P450 lAl levels or with B-Naphtoflavone (B-NF) and TBT in order to investigate the effect of TBT on the induction response due to B-NF. TBT inhibited both the enzyme activities of the constitutive P450 lAl and the induction response of this cytochrome to B-NF which is the typical inducer of P450 lAI. Inhibition by TBT was significant at a dose of 8.1 mg TBT/Kg. Bearing in mind the environmental levels of TBT and the effect of TBT reported in this study leaves little doubt that TBT in the water column has a great potential to alter or modify the CYP lAl activity in fish. This has to be taken into account when using mixed function oxygenases as a biomarker in mixed contaminant situations where heavy metals and TBT are concurrently present with organic contaminants. Furthermore the effects of TBT on the bile fluorescence, the liver histology, microsomal protein yield, liver somatic index together with the distribution of TBT and its metabolites in various tissues were investigated. This work was part of a research project, partly funded by the Commission of the European Communities, through the MEDSPA programme under the contract number MEDSPA- '91 - 1/UK//002/INT/06 and the Mediterranean Action Plan.
Description: M.SC.BIOLOGY
URI: https://www.um.edu.mt/library/oar/handle/123456789/64547
Appears in Collections:Dissertations - FacSci - 1965-2014
Dissertations - FacSciBio - 1966-2014

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