Cytotoxicity of mercury compounds in LLC-PK1, MDCK and human proximal tubular cells.

Six mercury compounds [HgCl2 (MC), Hg(CH3COO)2 (MA), Hg(NO3)2 (MN), C2H5HgSC6H4COONa (EMT), C6H5HgOCOCH3 (PMA) and CH3CIHg (MMC)] were studied using two kidney cell lines (MDCK and LLC-PK1), primary cultures of human proximal tubular cells (hPTC) and nonrenal cell lines (SAOS and Hep G2). Cell damage was measured with four different tests: neutral red uptake, mitochondrial dehydrogenase activity (MTT conversion), thymidine incorporation and protein content. Relative toxicity was established by the determination of the concentration of test compound inducing a 50% reduction of the parameter considered (EC50 value). Two groups could be distinguished: PMA, EMT and MMC are one order of magnitude more toxic than MC, MN and MA. Cellular uptake was measured by the HPLC-hybrid generation AAS after 24 hours treatment with 1.5 microM MC, MMC, PMA or EMT in MDCK cells, revealing Hg concentrations of 42.8 +/- 2.5 ng/mg protein for MC, 596.9 +/- 87.8 ng/mg protein for MMC, 269.8 +/- 75.7 ng/mg protein for PMA and of 115.9 +/- 25.2 ng/mg protein for EMT. Cytotoxicity was positively correlated with cellular uptake. The effect of the cellular GSH content on the toxicity of mercury was studied using the GSH synthesis inhibitor L-buthionine sulfoximine (BSO). In all cases an enhanced cytotoxicity was observed after BSO treatment. 2-Oxo-4-thiazolidine carboxylic acid (OTC) was used as a substrate for the GSH synthesis. Although OTC did not enhance the GSH content, the cytotoxicity of MC, MN and MA decreased significantly, no changes were observed for the other mercurials.(ABSTRACT TRUNCATED AT 250 WORDS)