Cadmium's mechanism of toxicity

Charles Miller rellim at mailhost.tcs.tulane.edu
Fri Jun 2 14:42:33 EST 2000



Cadmium is a common environmental contaminant. A recent report suggests that
cadmium exposure causes ~7% of the renal dysfunction in the general
population (see L. Jarup, et al., Scand. J. Work Envir. Health 24
(suppl):1-51, 1998). The kidney is a primary target of cadmium toxicity.
Recent work from Curtis Klassen's group and others suggest that cell death
in renal tubular epithelium cells is due to apoptosis (a programmed cell
death pathway).   

At the molecular level, cadmium ions (Cd+2) bind to the sulfur (-SH) groups
of proteins, cysteine, and glutathione and inhibit the function of these
biomolecules. Cadmium ions block the function of a number of cellular
enzymes. Cd+2 can mimic calcium (Ca+2) to some extent. For example, Cd+2 can
deposit in bone and binds Ca+2 binding proteins.
' 

Cadmium can be a concern in foods such as seafoods and "organically" grown
livestock, vegetables, and fruits. Reclaimed sewage sludge, manure, and
other sources of natural nitrogen fertilizers often contain excess metals.
Increasing levels of metals build up with with repeated application, and
lead to metal-contaminated food supplies.


There are a number of good toxicology textbooks (Casarett and Doull's
Toxicology, 5th ed.) and others as well as recent review articles available
through Medline (http://www.ncbi.nlm.nih.gov:80/entrez/query.fcgi?db=PubMed)
using the kewords "cadmium AND toxicity AND review". You can also check out
the bionet.toxicology FAQ for this group to find online sources at the ATSDR
and EPA web sites.

Best wishes,

Chuck Miller


--

Charles A. Miller, III, Ph.D.
Associate Professor of Environmental Health Sciences
Tulane University School of Public Health and Tropical Medicine
1430 Tulane Ave.
New Orleans, LA 70112
(504)585-6942    rellim at mailhost.tcs.tulane.edu



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Kathleen wrote...

Several days ago the New York Times had a story about hundreds of tons of
zinc sulfate imported from China for use in plant and animal fertilizers,
which was determined to be "heavily" contaminated with cadmium. Not all of
the contaminated ZnSO4 has yet been tracked, and this is not the first time
this has happened, according to the article.

I am not a toxicologist, but this story piqued my curiosity about the
mechanism of cadmium's toxicity, partly because all of the references
I checked merely told of its being harmful to all cells, very harmful to
liver and kidneys, and so forth. But what I'd like to know is how it does
its dirty work? What aspect of cellular metabolism does it interfere with?
Should I be searching out a toxicology text for this answer, and if so,
can someone recommend something suitable for one with a non-focused
general biology (with limited chemistry) background?

Thanks for any leads.

Kathleen 


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