CORRELATION OF POLYCHLORINATED DIBENZODIOXIN LEVELS WITH HEPATIC MIXED-FUNCTION OXIDASE INDUCTION IN GREAT BLUE HERONS

As part of the Canadian Wildlife Service monitoring of great blue herons in B.C., pairs of eggs were collected from 3 colonies with low, intermediate and high levels of PCDD and PCDF contamination: Nicomekl, U.B.C. and Crofton, respectively. One of each pair of eggs was used for chemical analysis by G.C.-M.S.; the other was hatched. Liver microsomes were prepared from the heron chicks and used for determination of cytochrome P-450 dependent assays (pmol/min/mol cytochrome p-450). Ethoxyresorufin-O-dealkylase (EROD) activity in the control Nicomekl group was 733 ± 181. The EROD activity in the herons from the Crofton colony was 2.6 fold higher (1882 ± 202) than the Nicomekl group. The U.B.C. colony was intermediate (1265 ± 161). No differences among the 3 heron colonies was found in pentoxyresorufin-O-dealkylase activity (Nicomekl: 650 ± 200; U.B.C.: 912 ± 146; Crofton: 1098 ± 109). Embryos of the paired heron eggs from U.B.C. and Crofton contained 13.5 and 20 times the levels of 2,3,7,8-TCDD compared to the Nicomekl group. The Crofton embryos contained higher levels of several other contaminants also. A highly significant correlation (p < 0.001) was found between EROD and 2,3,7,8-TCDD. The correlation coefficient did not change when EROD was compared to total chemical contamination using several toxic equivalency factors. Multiple regression analysis resulted in only one predictor variable for EROD: 2,3,7,8-TCDD. © 1990.