MSU Professor Earns Bowditch Award For Work On Hypertension

Main Category: Hypertension
Article Date: 27 Mar 2008 - 2:00 PDT

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The American Physiological Society has awarded Michigan State University Professor Stephanie W. Watts the 2008 Henry Pickering Bowditch Memorial Award for early-career achievement. The award goes to a scientist younger than 42 years whose accomplishments are both original and outstanding. It is the Society's second-highest award

Dr. Watts, a professor of pharmacology and toxicology, has focused her research on whether serotonin (5-HT) plays a role in hypertension. The story of her research is interesting not only because it is important to find a treatment for this serious illness, but because her research resembles a mystery novel, in which the detective has her eye set on a likely suspect, only to find out that the bad guy may be the good guy.

Dr. Watts will present the Bowditch lecture "The love of a lifetime: 5-HT in the cardiovascular system," on Sunday, April 6, at the APS session of Experimental Biology in San Diego. An audio of the interview may be found at http://www.lifelines.tv.

A silent killer

One-quarter of American adults suffer from hypertension, also known as high blood pressure. In hypertension, the blood vessels constrict, but because the body must transport the same amount of blood, it causes the blood to flow under much greater pressure.

This places greater strain on the heart and the blood vessels and can also damage the organs and tissues that receive the blood, including the brain, heart and kidneys. The disease is known as the silent killer because many people do not know they have the disease until it causes serious health problems.

Most of the body's serotonin, about 90%, is made in the gastrointestinal tract, where it plays a role in digestion by helping the smooth muscle of the intestines move. The remaining 10% of the body's serotonin is produced in the brain, where it plays a role in elevating mood, signaling food satiety and regulating sleep cycles.

The body needs tryptophan, obtained through the diet, to make serotonin. Tryptophan is found in a variety of foods, including poultry.

Still a hypothesis

Years of research have yielded this about serotonin's effect on blood vessels:

- the blood vessels of hypertensive individuals are very sensitive to serotonin
- hypertensive individuals have higher levels of serotonin in their blood

Molecules, known as transporters, carry serotonin to receptors in various parts of the body. Different receptors cause serotonin to do different things. There are at least 17 such receptors in the human body, making it difficult to unravel exactly how serotonin works.

Dr. Watts hypothesized that since it takes less serotonin to make hypertensive blood vessels contract, that hypertensive individuals may have a higher number of receptors. This could explain why the blood vessels of hypertensive individuals react more strongly to serotonin. She experimented with one receptor and found that blocking it reduced blood pressure.

In 2006, Dr. Watts gave serotonin to both hypertensive and normal rats, reasoning that serotonin would raise blood pressure in the non-hypertensive rats and that the rats with hypertension would experience an even greater rise in blood pressure. Instead, the serotonin reduced blood pressure by 15-20% in the non-hypertensive rats and by 33% in the hypertensive animals. Dr. Watts' lab has repeated the experiment with the same results.

The serotonin puzzle

So what to make of this latest clue, that serotonin lowers blood pressure when it's given to both hypertensive and non-hypertensive rats? These results have Dr. Watts wondering if serotonin levels rise because serotonin is trying to reduce blood pressure.

"I'm wondering if hypertensive people have higher level of 5-HT because that's a good thing," Dr. Watts said. "Now we're trying to figure out the multiple ways 5-HT can play with the cardiovascular system to cause these results."

One possibility is that once an individual suffers hypertension, it changes how the blood vessel works, toughening vessels to handle the higher pressure and changing how it reacts in the presence of serotonin. "It's really hard to tell which is the cause and which is the effect," Dr. Watts said.

When Dr. Watts presents her lecture, she hopes to get ideas from other physiologists who can help her resolve this puzzle. The lecture will take place at 5:45 p.m., Sunday, April 6, at the APS session of Experimental Biology 2008 in San Diego.

Note

The APS annual meeting is part of the Experimental Biology 2008 conference that will be held April 5-9 at the San Diego Convention Center. The press is invited to attend or to make an appointment to interview Dr. Watts. Please contact Christine Guilfoy at (301)634-7253 or at cguilfoy@the-aps.org.

Physiology is the study of how molecules, cells, tissues and organs function to create health or disease. The American Physiological Society has been an integral part of this discovery process since it was established in 1887.

American Physiological Society