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Refreshing Blood

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Replenishing stored blood’s nitric oxide may make transfusions more effective and less risky.


Transcript

Refreshing stored blood. I’m Bob Hirshon and this is Science Update.

Blood transfusions, while sometimes necessary, carry their own risk of organ failure, heart attack, and death. Case Western Reserve University cardiologist Jonathan Stamler suspects that’s because stored blood quickly loses nitric oxide. That’s a chemical signal that opens tiny blood vessels. Without it, the blood can’t deliver oxygen to tissues. In fact, when Stamler’s team gave transfusions of stored blood to animals, the oxygen levels in their tissues actually went down.

Stamler:
Whereas renitrosylated blood, blood restored in its nitric oxide levels, improved oxygen delivery to tissues. 

They also found that ordinary stored blood damaged kidney function, but nitric oxide-infused blood protected it. Stamler adds that the process of refreshing stored blood with nitric oxide isn’t very expensive, and could prevent many otherwise lifesaving transfusions from backfiring. I’m Bob Hirshon for AAAS, the Science Society.


Making Sense of the Research

Blood transfusions have long been a necessary, often lifesaving procedure. Without them, many victims of accidents and disasters would surely not be alive today. And yet, blood transfusions carry their own risks. Researchers have come to realize that people who get blood transfusions face a higher risk of heart attack, organ failure, and death than those with similar conditions who didn't require or get transfusions. As a result, doctors have become more conservative about giving blood transfusions, by giving them only when truly necessary, in the smallest amounts possible.

The basic function of blood is to deliver oxygen to tissues. When blood passes through the lungs, oxygen binds to a protein called hemoglobin in the red blood cells. The blood then circulates throughout the body, transferring this bound oxygen to organs and tissues. The red blood cells in stored blood can still pick up and transfer oxygen. So what's the problem?

Stamler's research suggests that the loss of nitric oxide from the blood may be to blame. Once blood is removed from the body, nitric oxide dissipates quickly, and it's virtually gone within a week. Blood is often stored much longer than that, though, so many blood transfusions are almost completely lacking nitric oxide, and almost all of them have less of it than blood circulating in the body.

Why does that matter? Nitric oxide acts as a chemical signal that opens up incredibly tiny blood vessels that deliver oxygen to some tissues. Some of these are so narrow that blood can move through them only one cell at a time. So there's not a big difference between having them opened and closed. And even a small nitric oxide deficiency—say, ten percent less than normal—may leave these blood vessels completely shut off more often than they should be, which means fewer blood cells deliver oxygen to tissues. That creates all kinds of health risks, since tissues and organs need oxygen to function.

Stamler's experiment showed that in animals, replenishing blood transfusions with nitric oxide could make the stored blood deliver oxygen just as well as normal circulating blood. If that can be applied to the general blood supply, it could improve the health and even save the lives of many blood recipients—an important outcome, since there's sometimes no substitute for replacing lost blood.

Now try and answer these questions:

  1. What are some of the risks of blood transfusions?
  2. How does blood deliver oxygen to tissues? What role does nitric oxide play in this process?
  3. In Stamler's experiment, nitric oxide-replenished blood got more oxygen to the animals' tissues and protected their organ function, compared to typical, nitric oxide-deficient stored blood. What if there had been no difference between the two? What conclusion would you draw? Would there be more than one possible explanation?
You may want to check out these related podcasts:

In Young Blood, hear how younger blood improved aging muscles in animals.

The Science Update Other Blood Types describes the discovery of a new way to classify blood, besides the common A/B/AB/O and Rh-positive/negative systems.

Donating blood may actually be good for you, according to the podcast Blood Cholesterol.


Going Further


For Educators

In Young Blood, hear how younger blood improved aging muscles in animals.

The Science Update Other Blood Types describes the discovery of a new way to classify blood, besides the common A/B/AB/O and Rh-positive/negative systems.

Donating blood may actually be good for you, according to the podcast Blood Cholesterol.

Worldwide, people donate 88 million units of blood—enough to fill 32 Olympic-sized swimming pools—annually. However, that meets less than 60% of the 150 million units needed each year. Learn more in this Science NetLinks Science Fact.


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