Cytopathology induced by mercuric chloride and methylmercury in cultured renal cells of the Atlantic spotted dolphin (Stenella plagiodon).

High mercury concentrations have been reported in various tissues of cetaceans, but the toxicological effects of mercury on cetaceans remain unclear. In vivo study is difficult due to the endangered status of these marine mammals and co-exposure to both mercury and selenium (antagonist of mercury) in the oceanic environment. The present data are the first ultrastructural information on dolphin renal cells exposed to mercury in vitro. Multiple organelle changes were observed in Atlantic spotted dolphin (Stenella plagiodon) renal cells treated with mercuric chloride (HgCl2) or methylmercury chloride (MeHgCl2). Mitochondria and rough endoplasmic reticula were swollen after treatment with HgCl2 or MeHgCl. Mitochondrial dense bodies and small cytoplasmic spherical granules of high electron density were also observed after exposure to MeHgCl. Cytoplasmic vacuoles and myelin-like figures were induced by both HgCl2 and MeHgCl. Nuclear changes included karyolysis, nuclear buds, and a novel observation in mercury-treated cells, vacuolization of (micro-)nucleoli after treatment with HgCl2. These morphological changes (multiple organelle damage and nuclear budding) indicated mercury-treated dolphin renal cells underwent oncosis and necrosis, and supported earlier pathophysiologic findings of diverse toxic actions on genetic, respiratory and other cellular functions.