Abstract
The frequencies of mitomycin C and cyclophosphamide-induced kidney and gill erythrocyte micronuclei were compared in Tilapia rendalli and Oreochromis niloticus. Cyclophosphamide (CP) and mitomycin C (MMC) were previously used to investigate fish sensitivity to micronuclei induction in kidney erythrocytes. Fish were treated with a single dose of cyclophosphamide (40 mg/kg) or mitomycin C (2 mg/kg). Peripheral blood samples and kidney blood samples were obtained, 1, 2, 3, 5, 7, and 15 days after the intra-abdominal injection of MMC. T. rendalli showed to be more sensitive than O. niloticus to micronuclei production. Both compounds were used at the maximum tolerated dose (MTD), and mitomycin C proved to be more toxic than cyclophosphamide. The frequency of micronucleated erythrocytes observed varied significantly among the treated individuals. The difference between the kidney and gill micronuclei frequencies was not significant. Higher levels of micronucleated erythrocytes were observed in Tilapia rendalli than in O. niloticus. T. rendalli produced erythrocytes with deformed nuclei, which O. niloticus did not.
Highlights
Fish serve useful as genetic models for the evaluation of pollution in aquatic ecosystems (Mitchell and Kennedy, 1992; and Park et al, 1993)
We analyzed the frequencies of micronuclei obtained from peripheral blood and from kidneis of Tilapia rendalli and Oreochromis niloticus, following induction by cyclophosphamide (CP) and mitomycin C (MMC) treatment
Mitomycin C at 2 mg/kg body weight was more toxic for O. niloticus than for T. rendalli, mainly between the third and the fifth post-inoculation days
Summary
Fish serve useful as genetic models for the evaluation of pollution in aquatic ecosystems (Mitchell and Kennedy, 1992; and Park et al, 1993). The erythrocyte micronucleus test has been used with different fish species to monitor aquatic pollutants displaying mutagenic features (De Flora et al, 1993). The micronuclei frequencies may vary according to the season, the kind of pollution involved, and the species of fish. The micronuclei represent acentric chromosome fragments or whole chromosomes lost during cellular anaphase. These structures are easy to visualize in erythrocytes and are often used as a measure of chromosomal aberrations (Rabello-Gay, 1991). Upon fish exposure to toxins, defective erythrocytes undergo passage from the kidney into the peripheral blood, from where they are removed by the hemocatheresis organs. We analyzed the frequencies of micronuclei obtained from peripheral blood and from kidneis of Tilapia rendalli and Oreochromis niloticus, following induction by cyclophosphamide (CP) and mitomycin C (MMC) treatment
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