Zn In Gills Research Articles

Alterations in Physiological Parameters of Rainbow Trout (Oncorhynchus mykiss) with Exposure to Copper and Copper/Zinc Mixtures

Rainbow trout (Oncorhynchus mykiss) were exposed to sublethal concentrations of copper (Cu, 14 μg/liter) and zinc (Zn, 57 and 81 μg/liter) for a 21-day period. The four treatments included a control, a Cu control, a Cu and low-Zn treatment and a Cu and high-Zn treatment. Selected parameters [e.g., hemoglobin (Hb), hematocrit (Hct), plasma glucose, lactate and cortisol, differential leukocyte count, respiratory burst, tissue metal concentrations, hepatic metallothionein (MT), brain acetylcholinesterase (AChE)] were evaluated at 2, 7, 14, and 21 days of exposure. Whole blood and plasma parameters were not altered by exposure to metals. The percentage of lymphocytes was consistently decreased in the three metal treatments, while percentages of neutrophils and monocytes were increased. Respiratory burst activity was elevated in all metal treatments. Gill Zn concentration was highly variable, with no significant alterations occurring. Gill Cu concentration was elevated above control levels in all metal treatments. Gill Cu concentration in the two Cu/Zn treatments was also elevated above levels in the Cu control. Hepatic metal concentrations and MT levels were not altered from control values. Measurements of brain AChE indicated an elevation in this parameter across metal treatments. In general, alterations in physiological parameters appeared to be due to Cu, with Zn having no interactive effect.

Naturally high levels of zinc and metallothionein in liver of several species of the squirrelfish family from Queensland, Australia

Recently, we found that liver of squirrelfish (Holocentrus rufus) from Bermuda contains remarkably high concentrations of metallothionein (MT) and Zn. To clarify the nature and cause of the Zn accumulation, four Holocentridae species from three genera (Neoniphon sammara, Sargocentron spiniferum, Myripristis violacea, and Myripristis murdjan) were collected from a totally different area, the Great Barrier Reef, Australia. The average hepatic Zn levels in these species ranged from 67 μg g-1 (S. spiniferum) to 1000 μg g-1 (N. sammara). The intraspecies variation in the hepatic Zn level was pronounced. In both N. sammara and M. murdjan, there was a 48-fold difference between the lowest and the highest Zn concentration. Zn accumulation was closely correlated to a dramatically elevated concentration of MT in liver. In N. sammara, which possessed the highest level of MT among the investigated species, the mean hepatic MT concentration was 19 500 μg g-1. Subcellular fractionation of the liver showed that MT was responsible for the binding of up to 74% of the hepatic Zn. The concentrations of MT and Zn in gills were low, suggesting that Zn storage in fish within this family is tissue-specific. The results further indicate that the high concentrations of MT and Zn in Holocentridae liver are linked to normal physiological processes. We suggest that the Holocentridae family may be a unique model for future studies of Zn metabolism and the function of MT.

Zinc content in organs of dogfish ( Scyliorhinus canicula L.) subject to sublethal experimental aquatic zinc pollution

1. Zn content of liver, pancreas, spleen, kidney, and muscle of zinc-treated and untreated dogfish were analysed. 2. Liver and spleen accumulate Zn after 14 days of treatment; liver, spleen and pancreas, after 25 days. 3. According to the Wilcoxon test, liver Zn accumulation was significantly higher than spleen at 14 days. The pancreas accumulate significantly more Zn than liver and spleen at 25 days. 4. Comparing the results with our work on the effect of Zn in gills, we conclude that when working in sublethal conditions (15 ppm) Zn toxicity would be bound to organs injury.