Researchers are usually trying to determine what can cause cancer at levels considered unacceptable, such as one more case of cancer per million people. But the age-old problem they have faced is that cost and laboratory logistics make it virtually impossible to test millions of rats at a time to see how many more cases of cancer appear when a compound is administered at a very low dose. So, scientists traditionally have raised the dose, tested it on a relatively small but affordable number of rats to see the results, and then extrapolated the results to determine one-in-a-million dosages that are considered unsafe.
"There have always been questions and criticism over use of this methodology, and that's one reason we've had to be conservative, to err on the side of caution," said Gayle Orner, an assistant professor in the Linus Pauling Institute at OSU. "When using rodents, it simply was not possible to study larger numbers of animals, the cost was too prohibitive."
What has changed, the OSU researchers said, is the realization that rainbow trout may for many purposes be as or more accurate in determining what compounds, at what levels, can pose a risk of human cancer. OSU has pioneered the use of trout for studies of this type for 40 years, and it may now be time to greatly expand the use of that research, the scientists said.
"We can do experiments with trout in large numbers at very low cost, about 5 percent of what a rodent study would cost," Bailey said. "For most studies of carcinogens, exposing 2,000 rodents would be a huge project. For us, working with 2,000 trout is a pilot study."
The OSU scientists recently completed the largest study ever done with animals in toxicology, exposing 40,800 trout to what's considered an "ultra-low" dose of dibenzo-a,l-pyrene, a chemical that can cause liver cancer and is part of a broad field of toxic compounds called poly
|Contact: George Bailey|
Oregon State University