Incubation mixtures (1.0 ml) contained 0.75 ml of appropriate HgCl₂ stock solution (0.05 μCi of ²⁰³HgCl₂, cold HgCl₂ to give a final Hg concentration of 0.1 μM and buffer or the indicated thiol compound at a final concentration of 0.4 μM) and 0.25 ml of PT cells (1.2 × 10⁶ cells/ml) in 1.5-ml microcentrifuge tubes. Mixtures were incubated at 37°C with shaking in a Dubnoff water bath for 1, 5, 10 or 60 min. Hg accumulation was stopped by centrifugation for 2 min at 13,000 × g. Supernatants were transferred to 2.0-ml cryovials with a 1.0-ml Hamilton gastight syringe. The syringe was rinsed with 0.5 ml of saline, and the rinse was added to the supernatant (total volume, 1.5 ml). Radioactivity in supernatants and cell pellets was then determined in a gamma counter. Results are the mean ± S.E. of measurements from four or five separate cell preparations.

• ↵1-a Significantly different (P < .05) from corresponding value in paired samples incubated with Hg alone (“buffer”).