Cytochrome P4501A immunoassay in freshwater turtles and exposure to PCBs and environmental pollutants

This is the result of a comparative study of cytochrome P4501A (CYP1A) induction in liver microsomes from three species of freshwater turtles. CYP1A induction in turtle hepatic microsomes was compared to CYP1A induction in microsomes from the alligator, Alligator mississippiensis. Treatment of two species of freshwater turtles with four consecutive intraperitoneal injections of 100 mg/kg Aroclor 1254 caused a four‐ to five‐fold increase in P4501A in hepatic microsomes of Chrysemys picta picta and Chrysemys picta elegans. The same treatment administered to another freshwater turtle, Mauremys caspica rivulata, resulted in a very low but significant (p < 0.01) induction of P4501A in hepatic microsomes. Specimens of M. caspica rivulata collected from an organic waste oxidation pond near the petrochemical industry area of the city of Ashdod exhibited normal levels of total hepatic microsomal cytochrome P450 but no detectable level of induction of cytochrome P4501A. The lack of P4501A1 induction could have resulted from two possible reasons. The first possibility is that the turtles were not exposed to residues of petrochemical waste in the pond. More likely, the apparent lack of induction resulted from the low response to CYP1A inducers found in this species. Induction of cytochrome P4501A was evaluated immunohistochemically in liver tissue of C. picta picta pretreated with Aroclor 1254 (400 mg/kg) or (124 mg/kg) 3,3′,4,4′‐tetrachlorobiphenyl. The most intensive staining was exhibited by sections of liver from a 3,3′,4,4′‐tetrachlorobiphenyl‐treated turtle. Staining of P4501A in liver sections from Aroclor 1254‐treated turtles was relatively moderate. In induced turtles, staining of the hepatocytes concentrated near the cell membranes and nuclear membranes, but stained granules were observed throughout the cytoplasm. The presence of inducible CYP1A enzymes in turtles is of importance from an evolutionary point of view and has potential ecological relevance.