Squirrels Shed Light on Human Hibernation

Compared to that most ubiquitous of all lab animals, the rat, the squirrel is truly remarkable. A rat's liver is virtually useless after 24 hours to 48 hours, Carey says.

"But in the ground squirrel, we found no damage at 24 hours, no significant damage at 72 hours, and we went to 96 hours of cold storage and found no apparent damage," she says. "To remain viable for four days is just unheard of."

But how does it do it?

To help find an answer, the Wisconsin researchers have turned to a third collaborator, Sandy Martin of the University of Colorado's Health Sciences Center in Denver. Martin, a molecular biologist, is comparing the composition of livers extracted from squirrels while they were hibernating with livers taken during the summer.

Her goal is to find out what's different, or what changed, in the liver as the animal prepared for hibernation. Specifically, she's trying to identify the proteins in the liver's cells.

"It's the proteins that really are the machinery of how cells work," Carey says. Some proteins must be introduced or altered to prepare the organ for hibernation.

Understanding the Extreme

Other research suggests that those proteins are the work of genes that are remarkably similar to genes in nonhibernating mammals, including humans. Researchers at North Carolina State University in Raleigh have linked complex proteins called enzymes to two genes. One enzyme breaks up fatty acids and converts them into usable fats for fuel for the hibernating ground squirrels. The other enzyme helps conserve the squirrel's glucose.

That research team, led by Matthew T. Andrews, who is now at the University of Minnesota, is attempting to identify the enzymes that preserve the organs during the long slumber, and prepare the organs for the sudden jolt of coming out of hibernation and returning to normal functions and body temperatures.

"Physicians could use that knowledge to develop new strategies for prolonging the shelf life of human organs intended for transplants or for helping humans suffering from starvation, muscle atrophy, hypothermia and hypoxia," Andrews says.

Of course, shelf life is only part of the problem with organ transplants. The larger problem is a lack of donors. About 6,000 Americans die each year while waiting for a transplant, according to the National Institutes of Health.

But prolonging shelf life could help ensure that donated organs remain viable until they can be transplanted, and it may well be that the secrets to that process are contained in a furry little animal that burrows under ground and likes to dine on dandelion seeds and grasshoppers.

Andrews has suggested that if we can ever fully understand how the ground squirrel gets through life, we should be better equipped to adapt to extreme environmental changes, and possibly even go into hibernation during long journeys to other planets.

Lee Dye’s column appears weekly on ABCNEWS.com. A former science writer for the Los Angeles Times, he now lives in Juneau, Alaska.

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