ASSESSMENT OF WITHIN-GROUP VARIATION IN CYP1A MESSENGER-RNA INDUCIBILITY IN ENVIRONMENTALLY EXPOSED AND CHEMICALLY TREATED ATLANTIC TOMCOD

CYP1A gene expression has been implicated in the processing of environ mental procarcinogens and levels of variation in CYP1 A mRNA expressio n are high in both environmentally exposed and chemically treated Atla ntic tomcod. The objective of this study was to evaluate the effects o f physical and biological parameters such as temperature, sex, and rep roductive state on within-group variation in CYP1A mRNA induction. Lev els of variation in CYP1A mRNA expression were directly correlated wit h mean levels of gene induction. Our results indicate that sex and rep roductive state, but not temperature, had significant effects on CYP1A mRNA inducibility in tomcod; however, these parameters did not accoun t for all interindividual variation in CYP1A inducibility. Other intri nsic biological factors, such as genetic polymorphisms in molecular pa thways leading to CYP1A induction, may contribute to the high levels o f interindividual variation in CYP1A inducibility in Atlantic tomcod.