Acclimation to Sublethal Aluminum: Modifications of Metal – Gill Surface Interactions of Juvenile Rainbow Trout (Oncorhynchus mykiss)

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Abstract
Juvenile rainbow trout (Oncorhynchus mykiss) were exposed for 21 d to one of three concentrations of H+and Al. Exposure to 27 μg Al∙L−1at pH 5.2 resulted in a significant internal physiological disturbance associated with the accumulation of Al at the gill, both of which declined with continued exposure. Increased resistance to an acutely lethal Al concentration (118 μg∙L−1, pH 5.2) was demonstrated by a reduction in both rate of mortality and in the magnitude of the internal physiological disturbance relative to controls at pH 6.5 or 5.2 and 0 μg Al∙L−1Both Al and H+were strong Ca2+antagonists causing modifications in the ability of the gill microenvironment to bind Ca2+during the acclimation exposures (saturation binding and competitive inhibition techniques used). The Al resistance was associated with a significant reduction in both the binding affinity of the gill surface for Al and the ability of Al to inhibit gill Ca2+binding. This reduction in the surface activity of Al in the fish with prior Al exposure suggested that increased Al resistance involved modifications in the chemical characteristics of the anionic groups present in the gill microenvironment, resulting in the reestablishment of membrane stability and electrolyte permeability.

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