Effect of prior, low-level cadmium exposurein vivo on metallothionein expression in cultured lymphocytes

Exposure to cadmium (Cd) is currently monitored by measurement of the metal in blood or urine, or by observation of excreted compounds such as beta 2-microglobulin or N-acetyl-beta-D-glucose. Whilst these approaches are useful for the detection of acute exposure to Cd, their applicability in the management of long-term, low-level exposure is less clear. Metallothioneins are ubiquitous proteins that are synthesized in response to heavy metal ions and may offer themselves as being a biologically sensitive indicator of Cd exposure. We have examined both basal and Cd-induced metallothionein mRNA levels in cultured lymphocytes from groups with different exposures to Cd, attempting to assess their potential as an indicator of Cd exposure and the suitability of such an assay for routine analysis. We found that induced metallothionein mRNA levels, rather than basal mRNA levels, increased in groups known to have received elevated body burdens of Cd, although these increases were not significant between groups. There was, however, a significant correlation between induced metallothionein mRNA levels and urinary beta 2-microglobulin. These results suggest that further work on the in vitro lymphocyte response to Cd as a diagnostic tool is warranted.