Toxicological effects of arsenic exposure in a freshwater teleost fish, Channa punctatus

Abstract

High concentration of arsenic in groundwater in the north-eastern states of India has become a major cause of concern. Inorganic arsenic of geological origin is found in groundwater used as drinking-water in several parts of the world. Arsenic is used in various industries and agriculture and excessive arsenic finds its way into lakes and rivers. Since arsenic is a known human carcinogen, the epidemiological studies are extremely important for this metal. Fish are ideal organisms to work with in toxicogenomics studies due to the strong power of fish models to establish biomarkers of exposure. Since, fishes respond to toxicants in a similar way as higher vertebrates, they can be used to screen for chemicals that are potentially teratogenic and carcinogenic to humans. Also fish absorbs dissolved or available metals and therefore can serve as indicator of metal pollution. The objectives of this work were to examine the toxicological effect and molecular changes caused by a heavy metal sodium arsenite (NaAsO₂), in Channa punctatus. When fishes were exposed to NaAsO₂, it induced death of the fishes in a concentration-dependent manner. 100 ppm, the highest concentration tested in this study, was found to be the deadliest and it induced death of the fishes within 18 to 20 h. As the concentration lowered the survival time increased dose dependently. Liver is the target organ of arsenic toxicity. Fish liver plays an important role in uptake, accumulation, bio-transformation and excretion of arsenic. We investigated the effect of NaAsO₂ on fish liver. NaAsO₂ was found to cause liver chromosomal DNA fragmentation and expression of certain proteins.

Key words: DNA Fragmentation, sodium arsenite, Channa punctatus.