Morphological evaluation of skin and intestine of fish exposed to black reactive dye 5

Abstract

The textile industry plays an important role in the economies of many countries. However, dyes used in the textile fibers are often resistant to biological treatment, implying the release of liquid waste. This represents an environmental and human health problem. Some dyes and their degradation products, especially the azo group, are mutagenic and carcinogenic. The skin and the intestine are important for homeostasis of the organism, arousing interest in toxicological studies. Thus, we aimed to evaluate the morphology of the skin and intestine of fish exposed to Black Reactive Dye 5. For the toxicological test, 24 animals, Danio rerio, were divided into four groups: Control (tap water); I (6 ppm); II (8 ppm) and III (10 ppm). Whole animals were fixed and decalcified for histological and immunohistochemical techniques. Morphometric analyzes were performed in the small intestine and in the skin of the ventral region. There were no deaths during experimentation, the fish maintained normal swimming and feeding behavior. In all animals, the intestinal and skin tissues presented architecture without modifications, necrosis, apoptosis, edema, and loss of adhesion. The skin presented increased mucous cells and skin thickness (p<0.05). In the intestine, an increase in intestinal villi, proliferating cells and goblet cells was observed (p<0.05). Through the present work, it was possible to confirm the sublethal of the concentrations studied and it was demonstrated that this exposure to PR5 dye causes slight alterations to the studied tissues.