CYTOCHROME-P450 AND CONTAMINANT CONCENTRATIONS IN NESTLING BLACK-CROWNED NIGHT-HERONS AND THEIR INTERRELATION WITH SIBLING EMBRYOS

Hepatic cytochrome P450-associated monooxygenase activities were measu red in 11-d-old nestling black-crowned night-herons (Nycticorax nyctic orax) collected from a reference site (next to Chincoteague National W ildlife Refuge, VA, USA) and three contaminated sites (Cat Island, Gre en Bay, WI, USA; Bah Island, San Francisco Bay, CA, USA; and West Mari n Island, San Francisco Bay, CA, USA). Arylhydrocarbon hydroxylase and benzyloxyresorufin-O-dealkylase activities of nestlings from contamin ated sites were only slightly elevated (less than threefold) compared with the reference site. Organochlorine pesticide and total polychlori nated biphenyl (PCB) concentrations in nestlings were greatest at cont aminated sites, although much lower than found in concurrently collect ed eggs and pipping embryos. Pollutant concentrations of nestlings wer e rarely associated with monooxygenase activity. In contrast, concurre ntly collected pipping heron embryos (often siblings of the nestlings) exhibited pronounced monooxygenase induction (means at contaminated s ites were elevated up to sevenfold and values of some embryos exceeded 25-fold induction). Furthermore, monooxygenase activity of pipping em bryos was significantly correlated with total PCBs, arylhydrocarbon re ceptor-active PCB congeners, and toxic equivalents. The modest monooxy genase responses of heron nestlings suggest that this biomarker may ha ve only limited value during this rapid-growth life stage.