Of Yeast and Men (with apologies to Mr. Steinbeck)

Steven F. Arnold, Diane M. Klotz, Bridgette M. Collins, Peter M. Vonier, Louis J. Guilette, Jr., and John McLachlan Science 272;1418, 1489-1492 (June 7, 1996)

It was bad enough that Theo Colburn concluded in Our Stolen Future that environmental estrogens are threatening our fertility, survival and intelligence based only on a few anecdotes involving wildlife.

As you may remember from my earlier article on Our Stolen Future, ONE of the problems with Theo's theory is that, even if it's true that manmade estrogen-like compounds in the environment may compete with our own estrogens, the natural estrogens in our bodies outnumber manmade estrogens in our bodies by as much as 40 million to one -- this is according to Stephen Safe of Texas A&M University.

Now, researchers at Tulane University report that experiments on genetically engineered yeast cells show that a mixture of two weakly estrogenic chemicals can be far more potent than the individual compounds.

The researchers took yeast cells and engineered them to contain genes that code for a human estrogen receptor and a "reporter" protein that the cell makes when an estrogen-like compound binds to the receptor. The yeast cell culture turns blue when the chemical binds to the receptor and the intensity of the color reflects how strongly the receptor is activated.

Separate tests on four pesticides produced little result. But when the pesticides were combined activity was reported to shoot up by factors ranging from 160 to 1600. Lynn Goldman, head of the U.S. Environmental Protection Agency's Office of Prevention, Pesticides and Toxic Substances was quoted as saying that the Tulane findings could have "enormous policy implications" for EPA. Oh yeah?

Yeast cells are members of the Kingdom Fungi and are (obviously) biochemically quite different from humans. This difference is one reason why humans use yeast to make pizza crust and not just the other way around.

Given the raging debate about extrapolating the results of laboratory animal experiments to humans, isn't it even a BIGGER s-t-r-e-t-c-h to extrapolate the results of yeast experiments to humans? At least animals and humans are in the same Kingdom!

The real problem here is that McLachlan et al. are fueling the environmental estrogen hysteria, even though no human health effects from environmental estrogens have been shown to occur. Isn't this missing the forest for the trees?

Finally, I think the Tulane researchers should watch out for the PETA spinoff known as PETY -- People for the Ethical Treatment of Yeast.

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