Heteropneustes fossilis (Bloch) is a common fresh water air breathing fish available in India. Due to continuous use in agriculture, the fish is constantly exposed to urea. The work was carried out to study the effect of this inorganic fertilizer on the liver protein of H. fossilis. The fish were exposed to 0.0078, 0.0156, 0.03125, 0.0625, 0.125 mg.l-1 concentration of urea for 7 and 14 days. Fish of both treated as well as control groups were killed by a severe blow on the head and liver was isolated for total protein estimation. Lowry et al (1951) was followed for protein( no particular protein was isolated, total amount protein which present in the extraction was estimated) estimation. The experiment was replicated five times. The study revealed that the amount of protein increased in most of the doses, indicating the resistance capacity of this fish to the sublethal doses of urea.

Keywords: Heteropneustes fossilis; Urea; Sublethal doses; Liver protein.