Researchers from UC Davis and UC San Diego have discoveredthe physiological mechanism that may cause lungs to bleed in race horses. The findings also have implications for certain human lung diseases. Most thoroughbreds bleed from their lungs when exercising strenuously, some so much that they must be retired. Called exercise-induced pulmonary hemorrhage, the ubiquitous condition is a controversial problem in the horse-racing industry. New evidence, gathered by James H. Jones, an assistant professor of systemic physiology at the UC Davis School of Veterinary Medicine, implicates the unusually high pressures in each side of the heart. The chambers on the left side of a horse's heart need very high pressures -- nearly twice those of most mammals -- to pump blood through exercising muscles. The right chambers pump blood through the lungs on its way to the left side of the heart at pressures three-to-four times greater than those measured in other mammals. The raised pressures may cause vessels to break in the lungs, Jones says. John B. West, a professor of medicine and physiology, and Odile Mathieu-Costello, an associate professor of medicine, both of UC San Diego Medical School, recently found collaborating microscopic evidence in the walls of pulmonary vessels from horses. The phenomenon intrigues West, because he suspects a similar mechanism might cause high-altitude pulmonary edema in people. Jones will discuss the results at the comparative respiratory session on Thursday, April 9, 3:30 p.m., Anaheim Marriott, Grand Ballroom A/B. West's work will be exhibited simultaneously during the pulmonary blood-flow poster session Thursday, April 9, 3:30-4:50 p.m., Anaheim Convention Center, Hall C.