RESEARCHERS FIND CAUSE OF COLD SENSITIVITY
1/31/02
Raynaud's Phenomenon
COLUMBUS, Ohio - People who get icy-cold fingers and toes may have more
than just an aversion to winter weather.
Researchers have determined the cause of Raynaud's Phenomenon, a
debilitating disorder that leaves people with an extreme sensitivity to
cold temperatures, is due to a chemical reaction in the body.
According to Dr. Nicholas Flavahan, a researcher at the Dorothy M. Davis Heart and Lung Research Institute at The Ohio State University and a principal investigator of a recent study, people with this disorder are forced to avoid many day-to-day situations -- like walking outside without gloves in the winter or even opening the freezer door -- or they may have an attack. "The reaction to the cold can be so severe that many people affected by this disorder have to avoid spending time outdoors altogether during the cold winter months," he said.
Raynaud's Phenomenon is a peripheral vascular disease affecting nearly
10 percent of the U.S. population, mostly women. In healthy individuals, the blood vessels in the body's extremities constrict when exposed to cold in order to decrease skin blood flow and reduce heat loss. People with Raynaud's Phenomenon have increased sensitivity to cold, meaning little or no blood travels to these areas, leaving fingers, toes, or ears, painful, cold and white in color. In extreme situations, the affected area can develop ulcers or gangrene.
In a study published in a recent edition of the journal Molecular
Pharmacology, Flavahan and his colleagues found, at room temperature,
the blood vessels constrict to control blood flow because of an
interaction between norepinephrine, a chemical produced in the body to
maintain normal blood pressure, and Alpha-2A receptors, proteins
normally found on the surface of cells in the blood vessels. "Our bodies
continuously use norepinephrine and these receptor proteins to control
blood flow and to maintain blood pressure," said Flavahan. "For instance, when we stand up, blood pools in our lower extremities. The
body then uses norepinephrine and receptor proteins to maintain blood
pressure so that we don't faint."
Flavahan and colleagues found that, when the temperature of cells
decreases, another type of receptor protein, called Alpha-2C receptors,
moves to the surface of the cell and starts interacting with norepinephrine. This interaction causes blood vessels in the extemeties
to constrict when they're cold, reducing needed circulation in the vessels. When Flavahan prevented the interaction between norepinephrine
and the Alpha-2C receptors, the skin's blood vessels no longer responded to cold and the blood vessels did not constrict. "These Alpha-2C receptors are amazing - they don't work well at normal temperatures, but absolutely love the cold!" said Flavahan. "That means that targeting their function should be a great therapy for Raynaud's Phenomenon.
Because we only use them when we're cold, blocking their function should have little or no side-effects." Flavahan hopes that with such therapy, warm blood flow will be maintained to icy fingers and toes and that Raynaud's Phenomenon will be prevented.
About three percent of the population who has Raynaud's Phenomenon,
later develops scleroderma - which is a life-threatening illness.
Scleroderma affects and ultimately shuts down vital organs and tissues
in the body. Symptoms of this disease include hard, shiny and wax-like
skin. The reason why certain people who have Raynaud's later develop scleroderma is still unknown. "Through this and ongoing studies, we hope to be able to understand the causes of scleroderma,"
said Flavahan.
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