Effect of zinc on thymocyte apoptosis.
(A) The effects of in vitro addition of zinc sulfate (200 μM) on the apoptotic index of murine thymocytes are shown. Freshly isolated murine thymocytes from 10- to 12-week-old male BALB/C mice were incubated for 24 hours with control (PBS), CP20 or DFO (300 μM IBE), or dexamethasone (10−7 M) prior to be analyzed for apoptosis by flow cytometry. Results are the mean ± SD of 6 independent experiments. (B) The effect of a high-zinc diet on in vivo–induced apoptosis and on the effect on intracellular zinc levels is shown. Mice were fed on either high-zinc or normal diets for 30 days and then administered either control (PBS) or CP20 (200 mg/kg) for 60 days while continuing their respective diets. At the end of this period, the animals were killed and their thymocytes removed immediately. Intracellular zinc levels were measured by the zinquin method and the proportion of cells undergoing apoptosis estimated by flow cytometry after 24 hours overnight in control medium at 37°C (RPMI 1640 medium containing l-glutamine and supplemented with 10% FCS). Results are ± SD of 8 mice on the same regimen.
