The emotional debate over whether genetically engineered food is safe to eat escalated yesterday with the publication of a controversial study showing possible health problems in rats that ate gene-altered potatoes.

Preliminary results of the study, which were leaked more than a year ago, have been a rallying cry for opponents of biotechnology in Europe, where there is widespread fear that gene-altered crops pose serious medical and environmental risks. This is the first time the results have been described in detail in a scientific journal.

But in a highly unusual twist, the editor of the journal has written a commentary revealing that several of the journal's own scientific reviewers considered the report to be unworthy of publication. They ultimately acquiesced, he writes, in part out of fear that biotech critics would accuse the journal of covering up a public health threat.

That confession has launched scientists into a heated discussion not only about the study results, but also about the decision to publish them.

The data are imperfect, writes Richard Horton, editor of the Lancet, the London-based medical journal in which the study appears, "but at least they are now out in the open for debate. Only by welcoming that debate will the standard of public conversation about science be raised."

On the contrary, said Charles Arntzen, president of the Boyce Thompson Institute for Plant Research at Cornell University. "There is general scientific outrage at the Lancet for publishing data that its own reviewers rejected as unscientific. If it was anything else, like a way to prevent heart disease or cancer, they would never publish shoddy work."

The research, led by Arpad Pusztai, then at the Rowett Research Institute in Aberdeen, Scotland, involved rats that were fed potatoes genetically engineered to produce an insect-repelling chemical. Pusztai and Stanley Ewen of the University of Aberdeen fed raw and boiled versions of the gene-altered potatoes to some rats; others dined on conventional potatoes that had been mixed together with the same insect-repelling compound.

Compared with the rats that were fed ordinary potatoes, those fed engineered ones for 10 days had significantly thicker intestinal walls, thinning of tissues in the large intestine and an increase in white blood cells in intestinal linings.

The researchers conclude that the gene-altering process somehow made the engineered potatoes toxic, because the insect repellent caused few problems when added to ordinary potatoes. They suspect that the rats' intestinal changes--the medical significance of which remains uncertain--may have been caused by the viruses that scientists used to get the new genes into the potatoes, or by normal potato genes that may have been disrupted when the repellent's genes were inserted.

The study is one of very few that have looked with such detail at the effects of eating genetically engineered food, but it comes with a lot of troubling baggage.

Pusztai first announced the results in August 1998 in an interview with British television--a move that made him a hero among anti-biotechnology activists but left him scorned by scientific colleagues, because the work had not been reviewed or accepted for publication. Pusztai was fired soon after.

Since then he has become something of a martyr among anti-biotech activists.

The insect repellent engineered into Pusztai's potatoes is a plant-derived compound called the snowdrop lectin. It has not been engineered into any of the approximately 40 commercial varieties of gene-altered crops that have been approved for marketing. And it is not related to the bacterially derived insect toxin that has been spliced into several approved varieties of genetically engineered corn and soybeans marketed and consumed in the United States since 1996.

In a critical commentary appearing in the same journal, Dutch researchers write that the Pusztai study involved too few rats, lacked proper controls and does not show that the intestinal changes were caused by the genetic modifications.

Even if the changes are worrisome, that's not a reason to reject the technology overall, said Libby Mikesell of the Biotechnology Industry Organization in Washington. "If something like this were to come through the U.S. regulatory system, . . . it would be subject to all kinds of toxicity tests and would go no further," she said.