MUTAGEN CONTENT AND METABOLIC-ACTIVATION OF PROMUTAGENS BY MOLLUSKS AS BIOMARKERS OF MARINE POLLUTION

Organisms combat pollutants by inducing biotransformation pathways, wh ich can be used for biomonitoring. Several parameters-biomarkers-chang e in stressed organisms or populations at different organisation level s. Molecular or cellular biomarkers are early-warning indicators of po llution. Xenobiotics are first biotransformed by phase I enzymes and t hen conjugated with endogenous metabolites by phase II enzymes. Many o rganic xenobiotics are initially biotransformed by cytochrome P4501A1; in mammals, it is induced by pollutants via Ah receptor, although in marine invertebrates, its inducibility is much more equivocal. Metallo thioneins are small Cys-rich proteins which bind transition metals; th ey detoxicate pollutant metals and are clearly induced in metal-expose d marine invertebrates. Some pollutants are genotoxins or can be conve rted into them. Determination of mutagens in bivalve molluscs followin g extraction with solvents and assay of mutagenicity with bacterial te sts is a useful biomarker for marine pollution. While some pollutants are directly mutagenic, others are only mutagenic after they are activ ated to mutagenic derivatives by monooxygenases or conjugative enzymes . Many of these catalysts are induced by xenobiotics; thus, increased activation of known promutagens can be used as biomarker of environmen tal pollution. Bioactivation of promutagens requires the simultaneous action of different pathways, thus, reproducing more closely the in vi vo situation than the specific assay of individual biotransforming enz ymes. Study of molluscs with different pollution levels indicates that polluted animals have higher capacity to activate 2-aminoanthracene a nd contain more apolar mutagens than those from reference areas. (C) 1 998 Elsevier Science B.V.