Scientists at the Johns Hopkins School of Medicine have observed that abnormally high levels of aluminum produce toxic changes in animal brain cells -- changes that may suggest a link between the metal and human diseases of the brain, such as Alzheimer's.
But Dr. Harvey Singer, a Hopkins neurologist, said yesterday that the experiment doesn't answer long-festering suspicions that aluminum causes Alzheimer's and a host of other brain disorders. Further research, he said, is needed before consumers should consider discarding their aluminum pots and pans.
"It lends further support to the [notion] that aluminum is a neurotoxin," said Dr. Singer. "Whether it plays a role in Alzheimer's has not been validated."
Using living cells formed through the fusion of rat and mouse brain cells, the scientists found that aluminum caused changes in levels of chemicals responsible for communicating messages from one cell to the next. The changes are similar but not identical to those observed during autopsies in the brains of people who suffered from Alzheimer's.
Dr. Singer said the test-tube cells, although not identical to human cells, are useful because they display many of the properties of human nerve cells -- particularly the manner in which they chemically send messages. The living cells were developed by the National Institutes of Health.
In the study, reported in the December issue of the journal Brain Research, scientists exposed the living cells to different amounts of aluminum for four to eight days, then compared the cells to others not treated with the metal.
The aluminum changed the levels of two chemicals responsible for sending and receiving messages and caused structural damage in proteins found within the test-tube cells. Abnormalities in the proteins, known as neurofilaments, and in the chemical messenger system, known as the cholinergic system, have both been observed in autopsies of humans with Alzheimer's.
Autopsies also have revealed abnormally high levels of aluminum in the brains of people who suffered from Alzheimer's and other brain disorders, including amyotrophic lateral sclerosis -- Lou Gehrig's disease. But scientists have never proved that excess aluminum actually causes the diseases.
People are exposed to aluminum through many sources, including purified water, antiseptics and antacids. But Dr. Singer said he doesn't know how much aluminum might be necessary to cause neurological damage in humans -- if it, indeed, causes any damage at all.