No Oxygen? The Naked Mole Rat Might Not Care


And, the award for strangest mammal goes to …

If there were such a prize, the naked mole rat could well win it.

For one thing, it’s naked. Not that most other animals wear clothes, but quite a few have noticeable hair or fur. The mole rat is, you might say, pinkly, wrinkly.

They are coldblooded, which seems wrong. No other known mammal is.

They live in underground tunnel complexes in colonies of hundreds led by a queen with a few male consorts, and lots of workers and soldiers. Doesn’t sound like a lion or a lamb, or even a platypus.

Until recently scientists thought they never got cancer. Then two mole rats in a lab were found to have it. Still, there are a lot of mole rats in the world and only two known to have cancer.

And now the latest twist in the can-you-believe-what-naked-mole-rats-do story is that the animals can survive for 18 minutes with no oxygen. None.

They can live for at least five hours in an atmosphere that is only 5 percent oxygen (the normal level is about 20 percent). Mice last about a minute with no oxygen and about 15 minutes in 5 percent oxygen.

Thomas Park at the University of Illinois, Chicago, said that five hours was an arbitrary cutoff, and that he didn’t know how long they might go. He does know that with no oxygen, 30 minutes was too long. They did not recover.

Dr. Park, who has studied the animals since 1999, worked with an international team of scientists to uncover this mole rat secret. He and Jane Reznick and Gary R. Lewin at the Max Delbruck Center for Molecular Medicine in Berlin and other researchers in the United States, Europe and Africa, reported their findings in Science on Thursday.

The researchers used a variety of tests on the mole rats’ brains and other organs to determine what was going on with the animals’ physiology.

Mole rats are a bit like hybrid cars in that they switch one form of energy metabolism for another. Generally, they can run their cells on glucose, the usual way of mice, humans and all other mammals. That process requires oxygen, which is the whole point of breathing.

But mole rats can switch to a different kind of biochemical process that uses fructose — the sugar found in fruit and high fructose corn syrup — and that doesn’t need oxygen at all.

They don’t keep running at the same speed when they switch systems. They fall into a kind of suspended animation, with a much lower heart rate and breathing. But they keep going.

Other mammals, like people and mice, can metabolize fructose without oxygen, but only in a very limited way — in the intestine, for instance. Mole rats, however, have mechanisms and enzymes for emergency fructose use in all their organs, most importantly the brain and heart.

Mole rats probably evolved this ability because the tunnels they live in can be low in oxygen. In fact, when they all gather together to sleep, the ones in the center may run short on oxygen. It’s harder for them to wake up.

There’s no immediate use for this knowledge, but it is one of many aspects of mole rat biology that seem worth learning more about. Heart attacks and strokes cause damage when hearts and brains are deprived of oxygen. Since humans do have a similar ability in some tissues to metabolize fructose without oxygen, Dr. Park said, “in theory we could bring that online when need be.”

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