EFFECTS OF LEAD ON THE GROWTH AND DELTA-AMINOLEVULINIC-ACID DEHYDRATASE ACTIVITY OF JUVENILE RAINBOW-TROUT, ONCORHYNCHUS-MYKISS

Activity of delta-aminolevulinic acid dehydratase (ALA-D) in blood and organs is a biomarker of lead (Pb) contamination in fish. Because cur rent methods cannot measure the bioavailability of Pb, this biomarker may predict exposure more accurately than analysis of Pb concentration s in water. Juvenile fish are generally more sensitive to Pb than adul t fish, but due to their small size, analysis of ALA-D in blood and in dividual organs is difficult. By modifying the erythrocyte ALA-D proce dure, we developed a method to measure ALA-D activity on the supernata nt from the tissue homogenate of whole fish (juvenile rainbow trout, O ncorhynchus mykiss). Significant decreases in the activity of ALA-D in rainbow trout were observed after a 29-day exposure to 121 and 201 mu g Pb liter(-1), but not after exposure to 29 or 48 mu g Pb liter(-1). Pb also significantly reduced growth in fish exposed to 201 mu g Pb l iter(-1). (C) 1998 Elsevier Science Ltd. All rights reserved.