Induction of micronuclei in vitro by organochlorine compounds in beluga whale skin fibroblasts

Abstract

Beluga whales ( Delphinapterus leucas) inhabiting the St. Lawrence estuary are highly contaminated with environmental pollutants and have a high incidence of cancer. Environmental contaminants may be partly responsible for the high cancer incidence observed in this population. DNA damage plays an important role in the development of cancer. The micronuclei (MN) assay was used to test the genotoxic potential of organochlorine (OC) pesticides with and without external metabolic factor in skin fibroblasts of an Arctic beluga whale. Toxaphene, chlordane and p, p′-DDT induced significant ( p<0.05) concentration-response increases of micronucleated cells (MNCs). Statistically significant increases in MNCs, ranging from 1.7- to 5-folds when compared to control cultures, were observed for 0.05, 0.5, 5 and 10 μg/ml toxaphene, 2, 5 and 10 μg/ml chlordane and 10 and 15 μg/ml p, p′-DDT. Presence of exogeneous metabolic factor (S9) completely abolished the MN induction potency of chlordane and p, p′-DDT, and toxaphene induced MN formation at higher concentrations (0.5 μg/ml) than without S9 mix. The ecotoxicological significance of MN induction by low concentrations of toxaphene is unknown and do not imply that toxaphene is involved in the etiology of cancer in St. Lawrence beluga whales. However, because of the known genotoxicity of toxaphene and the long lifespan of beluga whales, it cannot be excluded that toxaphene may pose a long-term genetic hazard to the more contaminated whales of this population.