Chemicals & Human Health

Kidneys and Metals Problem Set

Problem 8: Examples of metals that harm the kidneys

For help to answer the question:

Itai-itai byo is a disease found among Japanese women. Scientists believe that it is caused by eating rice grown in soil containing _____________.
A. lead
B. mercury
C. cadmium
D. chromium


Cadmium, mercury, lead and chromium are all nephrotoxicants, metals that are toxic to the kidneys. Each causes problems in the tubules, but each works by a slightly different mechanism.

Lead causes damage in the tubules where it inhibits the functions of the mitochondria. Eventually the cells are not able to reabsorb substances like they are supposed to. Lead can also bind with proteins and form protein inclusion bodies.

Mercury causes problems by binding to the sulfhydryl groups on proteins. The kidney may mistake the protein with mercury on it for a cofactor called glutathione. The kidney normally filters glutathione out of the urine and retains it in the body. When it does this to the proteins with mercury bound to them, it effectively concentrates the mercury in the kidneys. The mercury can go on to react with other proteins and enzymes in the cells and can eventually kill the kidney cells, leading to diseases associated with kidney failure. Mercury can also damage the central nervous system.

Cadmium is found in some soils in very high concentration. In Japan, women who eat rice grown on cadmium rich soils have anemia, damaged kidney tubules, and bone and mineral loss. Scientists believe they understand some of the mechanisms by which cadmium causes damage. Normally cadmium is excreted from cells when it binds to a protein called metallothionein (CdMT). This serves to protect most cells from damage, but in the kidneys the cadmium metal-protein complex is easily absorbed in the tubules. Once inside the kidney cells, the cadmium is released from the MT protein and can accumulate to toxic levels.

Chromium moves around the body as Cr04 until it reaches the kidney. In the nephrons, it mimics PO4 and SO4. It is filtered out of the filtrate and reabsorbed by the tubule cells and becomes very concentrated. There it can interfere with ATP energy exchange and can become a corrosive acid. Both of these interfere with the kidney's normal functions.

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Kidneys and Metals Problem Set Chemicals and Human Health vocabulary the biology project

The Southwest Environmental Health Sciences Center
The Biology Project
The University of Arizona
Monday, February 22, 1999
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