Print edition: 
WASHINGTON — You don't think of pythons as big-hearted toward their fellow creatures. They're better known for the bulge in their bodies after swallowing one of those critters whole.
But the snakes' hearts balloon in size, too, as they're digesting — and now scientists are studying them for clues about human heart health.
The expanded python heart appears remarkably similar to the larger-than-normal hearts of Olympic-caliber athletes. Colorado researchers report they've figured out how the snakes make it happen.
"It's this amazing biology," said Leslie Leinwand, a molecular biologist at the University of Colorado Boulder, whose team reports the findings in today's edition of the journal Science. "They're not swelling up. They're building (heart) muscle."
Reptile biologists have long studied the weird digestion of these snakes, especially the huge Burmese pythons that can go nearly a year between meals with no apparent ill effects. When they swallow that next rat or bird — or in some cases deer — something extraordinary happens. Their metabolism ratchets up more than 40-fold, and their organs immediately start growing in size to get the digesting done. The heart alone grows a startling 40 percent or more within three days.
Leinwand, who studies human heart disease, stumbled across that description and saw implications for people. An enlarged human heart usually is caused by chronic high blood pressure or other ailments that leave it flabby and unable to pump well. But months and years of vigorous exercise give some well-conditioned athletes larger, muscular hearts, similar to how python hearts are during digestion.
So Leinwand's team — led by a graduate student who initially was frightened of snakes — ordered a box of pythons and began testing what happens to their hearts.
Now the question is whether the kind of growth pythons have could be spurred in a mammal with heart disease, something Leinwand's team is starting to test in mice with human-like heart trouble. They also want to know how the python heart quickly shrinks back to its original size when digestion's done.
