Scripps Howard News Service. An antimicrobial agent found in many shampoos, soaps and cosmetic products inhibits the development of nerve cell structures critical for transmitting signals between cells, according to a new study presented Sunday.

Prolonged exposure to low levels of the agent _ methylisothiazolinone (MIT) _ restricted the growth of connections in immature rat nerve cells grown in lab cultures, apparently damaging the machinery of an enzyme that coordinates cell-to-cell contact. The compound may have potentially destructive consequences for developing nervous systems, researchers from the University of Pittsburgh told a meeting of the American Society for Cell Biology.

"While more research is needed to determine what effect MIT would have in rodent models, both at the cellular level and in a developing nervous system, our results thus far suggest there is potential that everyday exposure to the chemical could also be harmful to humans," said Elias Aizenman, a professor of neurobiology at Pitt who has been studying MIT for several years.

"I realize it's a big leap to suggest there may be a parallel between environmental exposure and the noticeably higher rates of diagnosed childhood developmental disabilities, but I would caution that based on our data, there very well could be neurodevelopmental consequences from MIT," Aizenman added. "I would be particularly concerned about occupational exposure in pregnant women and the possibility of risk to the fetus."

MIT and related compounds kill harmful slimy bacteria that grows in wet environments, so they are often found in personal care products; paints and coatings; water-cooling systems; and factories that use water for manufacturing.

An EPA review of the chemical for industrial uses six years ago concluded it posed no significant threat to human health and Aizenman also has found no earlier published reports that the compound is neurotoxic.

Aizenman first came across the chemical several years ago when he was studying how a particular cell death pathway was activated. MIT actually uses a different pathway, but the researcher noticed that the compound was so commonplace that he went ahead with tests on rat nerve cells.

A 2002 report published in The Journal of Neuroscience found that 10-minute exposure to high concentrations of the agent was lethal to mature rat neurons.

The new research on immature cells used doses 100 times less than the levels used for that study, but exposed them for an 18 hour period.

Normally, when immature, developing nerve cells are kept in culture for that long they develop an axon, an extension from the cell body that's used for sending signals to other cells and several dendrites, projections that receive incoming information from other cells.

But in the cells that were exposed to MIT, Aizenman and post-doctoral fellow Kai He found that the nerve cells had few, if any, of the extensions. Further tests showed that MIT significantly targeted an enzyme that's critical for starting molecular events in cell-to-cell contacts.

While the team members will continue their own cellular studies and living animal studies, they are hoping that other scientists will take up research to widen awareness of potential risks.

"This chemical is being used more and more extensively, yet there have been no neurotoxicity studies in humans to indicate what kind and at what level exposure is safe," Aizenman said. "Clearly, more study is needed, with both scientists and government regulators equally engaged."