Physiological and Biochemical Effects of Lithium in Rainbow Trout

The physiological responses of juvenile rainbow trout (Oncorhynchus mykiss) to lithium (as LiCl) in moderately hard freshwater (CaCO3 = 120–140 ppm, Na+ = ∼0.6 mM) were studied. The study employed a 15-day step-up exposure regime; 66 μg/L Li for the first 9 days and 528 μg/L for the next 6 days. The concentrations of plasma ions, apolipoprotein AI, total cholesterol, and fatty acids, as well as metabolic enzyme citrate synthase (CS) and Na+,K+-ATPase activities in the gill were measured. Li affected fish by exacerbated diffusive Na+ losses at the gills in the beginning of exposure and a decrease of branchial CS activity. Detrimental effects were shown in fish exposed to 528 μg Li/L. These included a reduction of gill Na+,K+-ATPase activity, possibly related to observed lower concentrations of free fatty acids and cholesterol in gill tissue.