New research has allowed scientists to determine how the skin's blood vessels play a significant part in the body's reaction to cold stimuli.
When the body responds to cold it cuts off circulation to the limbs to preserve blood flow to warm internal organs, but for some individuals the body's response may be too extreme or even arise misguidedly.
In conditions such as Raynaud's disease, the body reacts to cold or stress by narrowing the blood vessels in the fingers and toes, which in turn creates a numb sensation for the individual and the hands and feet eventually turning from white to blue to red.
Knowing this, researchers wanted to understand more about the physiological mechanisms.
Dr. Martin Michel, a professor at Johannes Gutenberg University in Germany, and the co-author of the editorial, told Healthday, "Our bodies are engineered by evolution to conserve heat and energy. One way of doing this is limiting blood flow to the skin by making blood vessels constrict, and norepinephrine (a hormone and neurotransmitter) does this via alpha-adrenergic receptors on muscle cells in the blood vessel wall. But we only want this to happen when it is cold." Senior study author Maqsood Chotani, a principal investigator at the Research Institute at Nationwide Children's Hospital, used muscle cells from tiny blood vessels in skin-punch biopsies from healthy participants as well as muscle cells from an artery found in mouse tails with circulation similar to human skin. Researchers identified new contributors that impact the function of the adrenergic receptor in small blood vessels.
"The alpha-2C receptors had been identified many years ago, but the exact function of this alpha-2C subtype in blood vessels was very intriguing to me," Chotani said. "Early observations showed the alpha2C to be inside the cell and not on the cell surface like other receptors in the same family. The general belief [had been] that the receptor doesn't do anything in blood vessels -- it was like a vestigial, or like a silent receptor." However the study found differently. According to the researchers, the alpha-2C receptors have a special role as a stress-responsive receptor, which conserves body heat. In conditions such as Raynaud's disease, there may be a dysfunction, where there is an over activity of receptors.
Michel hopes to observe the discovery of new mediators of blood flow control in order to understand the malfunction in those individuals.
For those individuals whose limbs are always hot, Chotani believes that is another physiological reaction from the blood vessels trying to open up and remove heat from the body to prevent it from overheating.