UO study is first to link histamine receptors to heat stress

Brett Wong is on a mission to help uncover the mechanism that regulates our ability to withstand heat stress. The goal is to help improve survival rates among those who suffer the most during heat waves: the elderly and people with conditions such as diabetes and heart disease.

The award-winning University of Oregon doctoral degree student’s research is the first to identify histamine receptors as contributing to increased blood flow during heat stress. Skin blood flow is a key factor in compensating for exposure to prolonged heat waves. “These are the same receptors that are involved in seasonal allergies for which people take antihistamines,” says Wong, who is the lead author on an article describing his findings in the November issue of the Journal of Physiology. Co-authors are Brad W. Wilkins, research associate, and Christopher Minson, assistant professor of human physiology and co-director of the UO Exercise and Environmental Physiology Laboratories.

Theirs is the first study designed to examine a potential role for histamine receptors in skin blood flow in humans. They tested the H1 and H2 histamine receptors and found that only the H1 receptor was involved in skin blood flow changes. The National Institutes of Health (Heart, Lung and Blood Institute) funded the study. “Many deaths in the Midwest have been associated with an inability to increase skin blood flow and regulate body temperature,” Wong says. “If we can understand the basic science behind increasing skin blood flow in healthy young individuals, we’ll be able to help at-risk populations.”

Led by Wong, the UO research team outfitted 11 human subjects in water-perfused suits and increased their core body temperature to about 100 degrees Fahrenheit. He threaded four hollow microfibers into the skin on their forearms and used microdialysis to target doses of nitric oxide or two types of antihistamines. Laser-Doppler flowmetry (LDF) was used to monitor changes in skin blood flow during heat stress. “I personally don’t like needles but it’s a very powerful technique to study skin blood flow,” says Wong, who knows firsthand what the subjects will experience, having tested the technique on himself.

A water-perfused suit is designed to tightly control skin temperature. The subjects wore a plastic coverall over the water-perfused suit, and the feet were wrapped in towels and plastic bags to minimize heat loss.

Current evidence suggests that sweating and increased skin blood flow (cutaneous active vasodilation) is mediated by the co-release of a neurotransmitter with acetylcholine from cholinergic nerves in the skin. However, the precise mechanism of action, and even the neurotransmitter itself, is unknown.

Earlier this year, Wong’s previous work in this area won the top national award for student research from the American College of Sports Medicine. The prize is given annually to only one student in the United States whose research is considered to be the most outstanding in the country.

Originally from Sierra Madre, Calif., Wong earned a bachelor’s degree from the University of California at Davis. His master’s degree is from the UO, and he expects to complete his doctoral degree in summer 2005. He plans to continue his research and eventually to teach in a university setting.