Characterization of an Unscheduled DNA Synthesis Assay with a Cultured Line of Porcine Kidney Cells (LLC-PK1)

Abstract

Proximal tubular cells are a primary site of tumour formation in the kidney probably due both to high exposure to absorbed chemicals and their multiple transport and bioactivation capacities (1). It is therefore important to develop appropriate short-term tests for investigating the organ specific genotoxicity of various chemicals. Since somatic mutations are considered as a crucial initiating step in chemical carcinogenesis (2), short-term tests detecting interactions of chemicals with DNA such as repair processes in damaged DNA sites are widely used for predicting potential carcinogenic properties of chemicals. The most appropriate method of estimating DNA repair is probably determination of unscheduled DNA synthesis (UDS) in exposed cells by monitoring the non-S-phase uptake of 3H-thymidine (3H-dThd) either by autoradiography of intact cells (3) or by liquid scintillation counting of the extracted DNA (4). UDS induction in renal tissue have already been undertaken using primary kidney cells exposed in vivo or in vitro to known or potential renal carcinogens and determining 3H-dThd incorporation by autoradiography (5). This method is highly specific, but its disadvantages lie in the long duration and the relative high costs of the experiments as well as in the difficulty of obtaining cell preparations of reliable and reproducible quality.