Methyl parathion (MP) is a commonly used organophosphorus insecticide, commercially available as Folidol 600. This chemical substance was tested to determine micronucleus (MN) frequencies in peripheral erythrocytes of the fish Cypnnus c e i o treated in vivo. The concentrations tested were 1.25,2.50,5.00 and 7.50 ppm. Fish were killed after 24 or 48 h of treatment. There was a significant increase in the frequency of micronuclei in the animals treated with 2.50 and 5.00 ppm after 24 h. At higher dosages this effect disap peared probably due to the increased cell lethality. The frequency of MN induction was lower at 48 than at 24 h after treatment. There was a dosedependent increase in MN frequency which, however, was significant only at the highest concentration (7.50 ppm) compared to control. RESUMENEl metil paratión (MP) es un insecticida organofosforado disponible comercialmente como Folidol 600. Esta substancia fue probada para determinar la frecuencia de micronúcleos (MN) en eritrocitos periféricos de peces Cyprinus ca+o tratados in vivo. Las concentraciones utilizadas fueron 1.25,2.50, 5.00 y 7.50 ppm. Los peces fueron sacrificados 24 y 48 h después del tratamiento. Se notó un aumento significativo en la frecuencia de micronúcleos en los animales tratados con 2.50 y 5.00 ppm y sacrificados después de 24 h. A concentraciones mayores este efecto desapareció probablemente debido al incremento de la letalidad celular. La frecuencia de inducción de MN fue menor después de 48 h que a 24 h del tratamiento. En la primera hubo una elevación en la frecuencia de MN dependiente de la concentración que, sin embargo, fue significativa cuando se comparó con el testigo solamente en la mayor (7.50 ppm).

The wing somatic mutation and recombination test (SMART) using Drosophila melanogaster was employed to determine the recombinagenic and mutagenic activity of four chemicals in an in vivo eukaryotic system. Two different crosses involving the wing cell markers mwh and flr(3) were used: the standard cross and a high bioactivation cross. The high bioactivation cross is characterized by a high constitutive level of cytochromes P450 which leads to an increased sensitivity to a number of promutagens and procarcinogens. Three-day-old larvae derived from both crosses were treated chronically with the oxidizing agent potassium chromate and with the three procarcinogens cyclophosphamide, p-dimethylaminoazobenzene and 9,10-dimethylanthracene. From both crosses two types of progeny were obtained: marker-heterozygous and balancer-heterozygous. The wings of both genotypes were analysed for the occurrence of single and twin spots expressing the mwh and/or flr(3) mutant phenotypes. In the marker-heterozygous genotype the spots can be due either to mitotic recombination or to mutation. In contrast, in the balancer-heterozygous genotype only mutational events lead to spot formation, all recombination events being eliminated. The oxidizing agent potassium chromate was equally and highly genotoxic in both crosses. Surprisingly, the promutagen cyclophosphamide also showed equal genotoxicity in both crosses, whereas p-dimethylaminoazobenzene was negative in the standard cross, but clearly genotoxic in the high bioactivation cross. 9,10-Dimethylanthracene showed a rather weak genotoxicity in the high bioactivation cross. Analyses of the dose-response relationships for mwh clones recorded in the two wing genotypes demonstrated that all four compounds are recombinagenic. The fraction of all genotoxic events which are due to mitotic recombination ranged from 83% (9,10-dimethylanthracene) to 99% (p-dimethylaminoazobenzene). These results demonstrate that the wing spot test in Drosophila is most suited to the detection of recombinagenic activity of genotoxic chemicals.

No abstract

No abstract