In vitro mercury-related cytotoxicity and functional impairment of the immune cells of rainbow trout ( Oncorhynchus mykiss)

Abstract

Cytotoxic and immunotoxic effects of mercury chloride and methylmercury on blood and head kidney leucocytes of rainbow trout ( Oncorhynchus mykiss) were evaluated in vitro, for a broad dose range (10 −4–10 −9 M Hg) of the chemicals. Mercury-related impairment of functional cellular parameters were measured using mixed leucocyte reaction (MLR) and mitogen stimulation of the cells by phytohaemagglutinin (PHA), concanavalin A (Con A) and lipopolysaccharide (LPS). Non-specific defense mechanisms of blood neutrophils and pronephros macrophages were analysed using flow cytometric assay of phagocytosis and respiratory burst. Impairment of the functional cellular activities appeared to be limited almost exclusively to cytotoxic concentrations of the mercurials. Similarly, phagocytic and respiratory burst activities of blood and head kidney phagocytes were markedly impaired by high, cytotoxic concentrations of the mercurials. The in vitro cytotoxic potential of methylmercury; ≥ 10 −5 M Hg, appeared to be at least ten times higher over the cytotoxicity of mercury chloride ≥ 10 −4 M Hg. At lower mercury concentrations, the data showed mostly normal- or above-normal values of the assayed functional activities of the cells. Overall, a nonspecific, poisoning-related impairment of leucocyte and phagocyte functions was concluded for the in vitro cytotoxic concentrations of mercurials.