Determining the lethal concentration LC50 96 h sodium nitrite and its impact on the liver tissue of white fish (Rutilus kutum Kamensky, 1901)

Nitrite is intermediate product in hydrogen natural cycle whose high rate of concentration level has toxic effects on fishes. In order to investigate this effect, the lethality range of this chemical was determined through initial tests. Then to determine the accurate LC50,180 piece of white fish with an average weight of 4/05 ± 0/8 g in 6 groups (5 experimental groups and one control group) were exposed to concentrations of 130, 144/5, 161/5, 180, 200 mg/l of sodium nitrite. The experiments were done based on static approach according to standard methods for 4 days (96 h). During the experiment dissolved oxygen, pH, total hardness and water temperature were measured and recorded daily. Average rate of lethality (LC50) of nitrite on white juveniles (Rutiluskutum) within 96 hours using Probit analysis was determined 146/62 mg/l. During this study, abnormal behaviors, such as unrest, swimming in the water level, and loss of equilibrium were observed. In order to observe histological changes in the liver, the tissue of torpid fish was examined at the end of each 24 h. After stabilizing the tissues in 10% formalin, 5-micron-thick tissue sections were prepared and stained using hematoxylineosin method. The most important observed liver lesions was, central venous bleeding, atrophy, hepatocyte necrosis, chronic focal necrosis, cloudy swelling and melanin and bile. The result showed that the Rutiluskutum was resistant to nitrite poison and the liver tissue can be exdamined as a biomarker of nitrite pollution index in this species.