Thallium Toxicity and its Interference with Potassium Pathways Tested on Various Cell Lines

Thallium (Tl) is a highly toxic heavy metal whose mechanism of toxicity is still not completely understood. The aim of this study was to test Tl cytotoxicity on several cell lines of different tissue origin in order to clarify specific Tl toxicity to a particular organ. In addition, possible interference of Tl with cell potassium (K) transport was examined. Human keratinocytes (HaCaT), human hepatocellular carcinoma (HepG2), porcine kidney epithelial cells (PK15), human neuroblastoma (SH-SY5Y) and Chinese hamster lung fibroblast cells (V79) were treated with thallium (I) acetate in a wide concentration range (3.9-500 µg/mL) for 24 h, 48 and 72 h. To assess competitive interaction between Tl and K, the cells were treated with four Tl concentrations close to IC₅₀ (15.63, 31.25, 62.50, 125 µg/mL) in combination with/or without potassium (I) acetate (500 µg/mL). The cells' morphology was monitored, and cytotoxic effect was assessed by 3-(4, 5-dimethylthiazole-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) test. The most sensitive to Tl exposure were SH-SY5Y cells, while HepG2 were the most resistant. The combined exposure to thallium (I) acetate and potassium (I) acetate for every cell line, except V79 cells, resulted in higher cell viability compared to thallium (I) acetate alone. The results of our study indicate that cell sensitivity to Tl treatment is largely affected by tissue culture origin, its function, and Na⁺/K⁺-ATPase activity.