Nephrotoxic effects of di-(2-ethylhexyl)-phthalate (DEHP) hydrolysis products on cultured kidney epithelial cells

1. Di-(2-ethylhexyl)-phthalate (DEHP) possesses a great industrial value as a plasticizing agent and has become an ubiquitous environmental contaminant. In most species it is rapidly metabolized to mono-(2-ethylhexyl)-phthalate (MEHP) and 2-ethylhexanoic acid (2-EHA). Evaluation of toxicity of DEHP and its primary metabolites has been focussed on reproductive toxicity and hepatocarcinogenic properties. The aim of this study was to determine the nephrotoxic potential of both DEHP metabolites by use of cultured kidney epithelial cells (Opossum kidney cells; OK cells). 2. For this purpose, OK cells were exposed for 3 days to MEHP and 2-EHA at concentrations ranging from 0.1 -500 micromol/L and the toxicity as well as the effects on migratory activity and intracellular cytoskeleton were studied by cell biological, morphological and morphometric methods. 3. When compared with corresponding controls, treatment of OK cells with MEHP and 2-EHA, respectively, showed marked differences in cell viability between both DEHP metabolites. MEHP caused a dose-dependent decrease in cell viability (ED50 = 25 micromol/L) accompanied by a moderate swelling of the cells at concentrations up to 25 micromol/L. MEHP concentrations higher than 25 micromol/L caused a dose-dependent shrinkage of the cells and the occurrence of a high amount of cell debris as a result of cell lysis. 2-EHA did not cause a reduced viability or an altered cell volume. The migratory activity of OK cells was not significantly influenced by both metabolites. Moreover, MEHP toxicity resulted in a largely reduced and altered organization of F-actin (stress fibers), but not of myosin, microtubules and vimentin. 4. The study indicates that cultured epithelial cells can be used as a prescreening system to assess the nephrotoxicity of hazardous substances such as DEHP. As demonstrated in this study, only MEHP, but not 2-EHA, has a marked nephrotoxic effect in vitro.