This is WEEKEND EDITION from NPR News. I'm Scott Simon.

Running marathons can help you build a healthy heart but there's a simpler way to cardiac fitness, as practiced by pythons. They just eat. A python's heart can rapidly grow by as much as 40 percent simply by devouring a huge meal.


SIMON: I have a little something in my throat just thinking about it. Now researchers think they've figured out how pythons perform this postprandial feat.

NPR's herpetology correspondent Joe Palca has the report.

JOE PALCA, BYLINE: Talk about sedentary; the Burmese python puts a couch potato to shame. To get a meal, pythons employ what scientists call a Sit and Wait foraging tactic. In other words, they lie around in a Burmese jungle and wait for the food to come to them. Perhaps not surprisingly, this can mean months between meals.

When they do eat, the meal can be huge - a 40 pound pig, for example - and suddenly, these sedentary snakes switch into metabolic high gear.

PROFESSOR STEPHEN SECOR: Imagine running a marathon for five days non-stop. That is what these snakes are experiencing metabolically when they're digesting a meal.

PALCA: Stephen Secor studies snakes at the University of Alabama, Tuscaloosa. He says all this digesting means the python's heart has to step up its game and pump a lot more blood to the snake's digestive system.

SECOR: So it responds like any other muscle that's, you know, experiencing chronic use. It grows.

PALCA: This is the same thing that happens to the hearts of long distance runners but to a much greater degree in the python.

SECOR: Within two to three days, you can get anywhere between a 30 and 40 percent increase in the mass of the heart.

PALCA: As the meal is digested, the heart returns to normal.

Leslie Leinwand became intrigued by the python. She's a molecular biologist at the University of Colorado, and she studies hearts but mostly mammalian hearts. She was a bit intimidated by studying pythons, and then she figured...



LEINWAND: Let's build a python colony here.

PALCA: With the help and advice of Stephen Secor, she built her colony of pythons and started looking for an explanation about why the heart growth occurs. The first clue came from the python's blood.

LEINWAND: Within 24 hours after feeding, the blood is like milk. There is so much fat in it that you can't see through it. I mean, it's completely opaque.

PALCA: This was obviously good fat, so Leinwand asked her junior colleague Cecilia Riquelme to find out what it was made of.

LEINWAND: Before she did that, though, she took a big leap, and did an experiment that I told her would never work, so she shouldn't bother doing it. And that's the wonderful thing about science - she ignored me and did it anyway.


PALCA: The experiment was to take blood from a postprandial python and inject it into a mouse. To Leinwand's surprise the mouse heart also increased in size.

LEINWAND: What that means is that it was more than of academic interest to people who study reptiles and pythons.

PALCA: It had implications for healthy heart growth in mammals, possibly even humans. As they report in the journal, Science, Leinwand and her colleagues have now figured out that it's a particular ratio of three fatty acids that hold the key. Simply by injecting the right ratio of these fatty acids into a hungry python, its heart would begin to grow.

Leinwand says she faced some skepticism when she started studying snakes.

LEINWAND: Most of my friends said, why are you doing this? You know, what is a python going to tell you that's relevant to a mammal? And I said just wait and see.

PALCA: Who'd have thought that pythons might hold the key to a healthy heart?

Joe Palca, NPR News, Washington.

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