MERCURY-INDUCED MICRONUCLEI IN SKIN FIBROBLASTS OF BELUGA WHALES

Beluga whales (Delphinapterus leucas) inhabiting the St. Lawrence estu ary are highly contaminated with environmental pollutants and have a h igh incidence of cancer. Environmental contaminants may be partly resp onsible for the high incidence of cancer observed in this population. DNA damage plays an important role in the development of cancer. The m icronuclei assay was used to test the genotoxic potential of mercury c ompounds in skin fibroblasts of an Arctic beluga whale. Both mercuric chloride (Hg) and methylmercury (MeHg) induced a highly significant (p < 0.001) dose-response increase of micronucleated cells. Statisticall y significant increases in micronucleated cells were observed for 0.5, 5, and 20 mu g/ml Hg and 0.05, 0.5, and 2 mu g/ml MeHg when compared to control cultures. Concentrations of 0.5, 5, and 20 mu g/ml Hg induc ed a two-, three- and fourfold increase of micronucleated cells, respe ctively. Treatment with MeHg was one order of magnitude more potent in inducing micronuclei and in inhibiting cell proliferation than Hg. Al though results of this in vitro study do not imply that mercury compou nds are involved in the etiology of cancer in St. Lawrence beluga whal es, significant increases in micronuclei frequency were found at low c oncentrations of MeHg (0.05 and 0.5 mu g/ml) that are believed to be c omparable to concentrations present in certain whales of this populati on.