Variability in micronucleus induction with different mutagens applied to several species of fish

Abstract

Fish are often used for screening genotoxicity of water. For such programs, a knowledge of the sensitivity to clastogens, spontaneous micronucleus frequency and cell cycle kinetics of the target tissue is necessary. To investigate the pattern of inter-specific sensitivity to micronucleus induction three species of fish, Tilapia rendalli, Oreochromis niloticus and Cyprinus carpio, were exposed to the clastogens bleomycin (BLM), cyclophosphamide (CP), 5-fluorouracil (5-FU), and mitomycin C (MMC). The binucleate/mononucleate ratio in peripheral erythrocytes exposed to cytochalasin B was also used to evaluate the time-dependent response of micronucleus formation during hematopoesis in the kidney and the micronucleus peak in peripheral erythrocytes. Micronucleus frequencies induced by CP were significantly greater than their respective controls for the three fish species throughout all treatment periods. During the whole evaluation period (30 days) CP was also the most effective clastogen. In general, until the 14th day of evaluation period T. rendalii was the most sensitive species to clastogens. No difference in micronucleus frequencies among species was observed in the 4th evaluation (at the 30th day). A micronucleus peak was observed at the 7th day after treatment. After the 14th day the frequencies were stabilized. The cytochalasin B experiment was carried out to demonstrate that micronuclei induced in the young kidney erythrocyte cells were detected in the circulating blood 2-4 days later.<br>Este estudo fez uma avaliação da indução de micronúcleos em eritrócitos de sangue periférico de peixes Tilapia rendalli, Oreochromis niloticus e Cyprinus carpio após o tratamento com mitomicina C, ciclofosfamida, 5-fluorouracil e bleomicina. Foram colhidas amostras periódicas de sangue com 2, 7, 14 e 30 dias após o tratamento único. Os tratamentos com citocalasina B tiveram como objetivo analisar as proporções entre células binucleadas/mononucleadas nos diferentes períodos de tratamento, para a comparação com os picos de micronúcleos entre as diferentes espécies, uma vez que o orgão hematopoiético nos peixes é o rim cefálico e o sangue analisado é de origem periférica, o que nos dá uma noção do tempo do ciclo celular dos eritrócitos. A análise das taxas de aumento das freqüências de micronúcleos ao longo do tempo demonstrou que do 2° ao 7°dias elas foram crescentes, decresceram ao 14° dia e mantiveram-se estáveis até ao 30°. Os 4 compostos químicos aumentaram significativamente as freqüências de micronúcleos ao longo de todo o período de tratamento, sendo que a ciclofosfamida e a mitomicina C foram as mais efetivas. A T. rendalli foi a espécie mais sensível a todos os tratamentos, enquanto que C. carpio foi a mais resistente. Entre 2 e 7 dias pós-tratamento observaram-se as maiores induções de micronúcleos. A partir do 14° dia de tratamento as freqüências de micronúcleos tenderam a diminuir e as diferenças entre as espécies não foram significativas

Comparison between the micronucleus frequencies of kidney and gill erythrocytes in tilapia fish, following mitomycin C treatment

“…Therefore, it is suggested that micronuclei tests in fish erythrocytes be carried out at various times following treatments, thus making it possible to follow-up the changing micronuclei frequencies. Studies of the micronuclei rates of various fish species showed that they generally peaked between the first and fifth days after treatment (Al-Sabti and Metcalfe, 1995;Grisolia and Cordeiro, 2000). We also conclude from this study that the sampling of peripheral blood is appropriate and sufficient for biomonitoring projects, as it allows to collect several samples from the same individual, without having to sacrifice it.…”

Évaluation de la cytogénotoxicité des sites de pollution du PONT et d’ACCRON de la lagune de Porto- Novo

“…Plusieurs études menées sur les eaux usées provenant des décharges industrielles ou urbaines ont démontré l'existence des activités génotoxiques (Grover et Kaur, 1999 ;Lah et al, 2004 ;Abdel-Migid et al, 2007 ;Junior et al, 2007). L'intérêt sans cesse croissant qu'on porte à la génotoxicité causée par les polluants environnementaux est dû au fait qu'il entraine le développement de différents tests biologiques utilisés pour la détection et l'identification des génotoxiquants dans l'air, l'eau et dans le sol (Grisolia et Cordeiro, 2000). Les tests de génotoxicité sont généralement utilisés pour évaluer le potentiel génotoxique dans l'environnement et au niveau des échantillons d'effluents industriels (Cotelle et al, 1999 ;Grover et Kaur, 1999 ;AbdelMigid et al, 2007).…”

Scenario of Genotoxicity in Fishes and Its Impact on Fish Industry

“…The selection of fishes as a model in the ecogenotoxicological studies could be made since fish is a very sensitive bio-indicator of water quality and can highlight the potential danger of new chemicals introduced in the aquatic environment (Bailey et al, 1992) and also respond to toxicants in a manner similar to higher vertebrates (Al-Sabti and Metcalfe, 1995). They have greater ability to metabolize xenobiotics and accumulate pollutants (Grisolia and Corderio, 2000). They are capable of inhabiting practically all zones of the aquatic habitat and have great commercial and recreational value (Solbe, 1993).…”