Calmodulin concentration in mucus of rainbow trout,Salmo gairdneri, exposed to combinations of acid, aluminum, and calcium

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As a result of increasing acidification in various watersheds elevated levels of aluminum have been observed in soil and surface water. The toxicity of Al to fish has been shown to be positively correlated with the concentration of inorganic monomeric. The exact mechanism(s) of Al toxicity is not fully understood. Recently, the presence of calmodulin (CaM), a calcium-regulating protein, has been reported in fish gills and mucus. Calmodulin selectively binds inorganic monomeric Al causing conformational changes in the protein. Aluminum-induced conformational changes cause a reduction in the ability of calmodulin to mediate Ca-dependent phosphodiesterase and ATPase activity. Calmodulin also plays a key role in coordinating the effects of secondary messenger systems in response to cellular stimulation. Given the involvement of calmodulin in numerous biochemical pathways, its interaction with aluminum may be a key lesion in the broadly defined syndrome of aluminum toxicity. The present study was undertaken to establish a relationship between Al concentration in aqueous solution and the quantity and activity of CaM in the mucus of adult rainbow trout (Salmo gairdneri). Fish were exposed to various levels of pH, Ca, and Al. Mucus was collected and the amount of CaM was determined. The ability of the Al-exposed CaMmore » to activate the phosphodiesterase enzyme system was also evaluated.« less