Growth and protein turnover during acclimation to acid and aluminum in juvenile rainbow trout (Oncorhynchus mykiss)

Growth, feeding, and protein synthesis (k_s) and degradation (k_d) in gill, liver, and whole body were measured in juvenile rainbow trout, Oncorhynchus mykiss, during 32 days exposure to sublethal acid (pH 5.2) and acid + aluminum (Al) (30 μg·L^-1) in soft water. The only effects observed for exposure to acid alone were depressions of gill k_s (17%) and k_d (27%) after 15 days (data not available after day 15). Exposure to acid + Al caused a loss of appetite, a 73% reduction in whole body growth rate, and a 36% reduction in whole body k_s during the first 7 days; all of these subsequently recovered, although mean body weight was still significantly depressed after 32 days. Gill k_s and k_d were greatly stimulated after 7 days and gill k_s remained elevated after 32 days, suggesting a chronic cost of gill repair and (or) acclimatory processes even after physiological recovery was achieved. However, this elevated cost was small relative to the whole animal protein synthesis budget. Other chronic effects included suppressed liver k_s and k_d, reduced whole body translational efficiency, and enlarged liver size. Conversion of food into growth was paradoxically increased throughout all stages of acid + Al exposure but may have been the result of reduced routine activity.