Confluent, hPT cell cultures were pretreated for 24 h with either media (= Control), 1 mM TRI, or 50 μM DCVC. Cells from the three pretreatment groups were then incubated for 1, 2, or 4 h with either 0, 0.25, 1, or 5 μM HgCl2. Cells were analyzed for apoptosis by flow cytometry as described in the legend to Fig. 8. Results are means ± SE of measurements from 3 separate cell cultures. *Significantly different (P < 0.05) from corresponding samples preincubated with media.