Feed-borne exposure to zearalenone leads to advanced ovarian development and limited histopathological changes in the liver of premarket size rainbow trout

摘要

To gain insight into the possible implications for aquaculture of the presence of ZEN in fish feed at the EC guidance level, we determined the effects of over two months of feeding of premarket size rainbow trout (similar to 250 g) with ZEN-contaminated feed at a dose of 1.81 mg.kg(-1) feed (90.5% of the current guidance value) under aquaculture conditions. After 37 and 71 days of the experiment, both control and ZEN-challenged fish were weighed and measured to assess their growth performance. To examine the health-related effects of ZEN exposure, fish blood was collected for biochemical measurements of plasma markers, and their livers and gonads were fixed for histopathological analysis. Additionally, to examine the effect of ZEN on the molecular background of fish reproduction, the mRNA level of vitellogenin (vtg) in the fishes' liver was determined. Finally, exposed fish tissues were analyzed for residual concentrations of ZEN and its metabolites in order to estimate the potential health risks for the fish consumers. Our results indicate that when premarket size fish are fed for two months with ZEN-contaminated feed at a concentration just below the EC guidance value, the growth of the fish is not affected. The analysis of residual concentrations of ZEN indicated that there was no threat to the health of potential consumers of the meat from the exposed fish. However, the residuals accumulated in the fishes' intestine and liver, and trace amounts of ZEN were also found in their ovaries. Although histological analysis of the liver cross-sections revealed structural irregularities in the treated group, including necrotic areas, disorders of polygonal hepatocytes, cytoplasm vacuolization, and macrophage aggregates, these developments were not accompanied by alterations in levels of plasma biochemical markers. This shows that ZEN had only a limited influence on the liver structure of the exposed fish. Although the experimental groups did not differ in terms of vtg mRNA levels, our results suggest that ZEN in feed may accelerate sexual maturation of the female fish, as ovarian development was more advanced in the exposed group. Our findings suggest that the presence of ZEN in fish feed may have consequences for aquaculture and warrant the need for further research in order to reassess the recommended limits.