BACKGROUND: Regulation of electrolytes levels and water in fish is very important because of its vast permeable surfaces that are in contact with the environment. Therefore, for homeostasis and osmoregulation, various adaptation mechanisms at different biological levels have  been developed. OBJECTIVES: The aim of this study was to determine the changes and adaptations of mitochondria-rich cells as an important cellular response to these changes.This was influenced by different environmental salinities in fish Sparidentex hasta which are very important economic species in the southern region of the country. METHODS: 180 fish, aged three months, 20 - 25 cm in length and weighing about 150 gr were exposed  directly to different concentrations of salt (5, 20, 40 and 60 ppt) for 1 week. Localization of the Na +, K +-ATPase in mitochondria-rich cells in gill epithelial were studied in different environmental salinities during the adaptation period.  was performed by using IgGα5 as immunohistochemistry method. RESULTS: NKA localization showed that the mitochondria-rich cells are in the filament and rarely in lamellar epithelium. Intensity reactive of the antibody used during the period showed an increase  in 5 and 60 ppt and decrease  in 40 ppt. CONCLUSIONS: Generally, tolerance and compatibility of Sparidentex hasta to salinity changes are due to rapid changes in mitochondria-rich cells to regulate the entry and exit of water and electrolytes. So to adapt with the new condition of environment some changes in the apical openings appear that regulate the amount of the carrier electrolyte enzymes in basolateral membrane. It also causes adaption of mitochondria activity to the new condition.

BACKGROUND: Tobacco (Nicotiana tobaccum) is a plant with piscicidal and fertilizing properties. OBJECTIVES: In this study the effect of different concentrations (0.1, 1, 10 and 100mg/l) of hydro-alcoholic extracts of tobacco has been examined on different tissues of Rainbow trout. METHODS: Samples from liver, kidney and gill of Rainbow trout were stained with hematoxylin and eosin and studied under light microscopy. RESULTS: Various histopathological lesions were observed in the liver of Rainbow trout exposed to different concentrations of tobacco. The results showed that with increase in concentrations of tobacco up to 10 and 100mg/l, bloodshed increased and hepatocytes lost their continuity and showed discontinuity mood. Lamellar aneurysm, bleeding and leukocytes infiltration, clubbing at the end of the lamellae, hyperplasia of secondary lamellar epithelium, epithelial lifting of secondary lamellae and creating an edematous space, lamellar shortening, vacuolation and lamellar fusion were the more abundant branchial lesions after exposure to tobacco. Separating the epithelium from basement membrane, hypertrophy, glomerular capillary dilation and tubular degeneration were observed in renal tissues in all treatments. At higher concentrations of tobacco (10 and 100mg/l), renal tubular necrosis was also observed. According to the results liver of rainbow trout showed a few histopathological alteration following exposure to tobacco extracts. Unlike the liver, gills of rainbow trout due to direct contact with pollutants showed more lesions. CONCLUSIONS: Tobacco extract has more pathological effects on gills in comparison with liver and kidney of Rainbow trout due to direct contact with the dissolved pollutant.