Variations in liver histology and P-gp expression among fish species in Doce River Basin, Brazil: implications for pollution sensitivity.

Fish may have different sensitivity to pollutants present in the water. We analyzed the liver histology, and P-gp expression in six species of fish from the Doce River basin. Fish were caught at six different points in the Doce River, and liver samples were taken for histological analysis. P-gp expression was analyzed using an immunohistochemical technique. In Astyanax lacustris, Hoplias intermedius, Hypostomus affinis, Trachelyopterus striatulus and Oligosarcus acutirostris, a double arrangement of hepatocyte plates was generally observed (tubular-form), while in Deutorodon taeniatus, a single arrangement of hepatocyte plates was frequently observed (cord-like). Histological changes, such as cytoplasmic vacuolation and nuclear alteration, were observed in the livers of all species analyzed, however, the species A. lacustris (34.1%) and H. affinis (33.3%) were those with the fewest individuals with histological changes. The H. intermedius, T. striatulus, and O. acutirostris were the species that presented more than 80% of their individuals with histological changes. The A. lacustris and H. affinis were the species that showed the highest P-pg immunolabeling in the liver, while the T. striatulus and O. acutirostris had the lowest levels. These results support the hypothesis that levels of P-gp expression could respond to the resistance or sensitivity of each species to environmental pollutants.