Louis J. Ignarro

Louis J. Ignarro, born in 1941, American pharmacologist and Nobel laureate who helped illuminate the cardiovascular role of nitric oxide (NO), a gas produced in the cells of humans and other organisms. Ignarro was among the first to suggest that NO serves as a molecular signal—a substance that is released by one cell and influences the function of another cell. He also helped identify NO as a crucial agent in the process by which blood vessels widen, or dilate. Scientists now recognize that NO not only regulates blood pressure and other cardiovascular functions but also plays a role in many other processes. Among these processes are helping the body fight bacterial infection and sending messages between cells in the nervous system.

Born in Brooklyn, New York, Ignarro earned his bachelor’s degree in pharmacy from Columbia University in 1962. He earned his Ph.D. degree in pharmacology in 1966 from the University of Minnesota. Between 1979 and 1985, Ignarro was a professor in the pharmacology department at the Tulane University School of Medicine in New Orleans, Louisiana. Since 1985 he has been a professor in the Department of Molecular and Medical Pharmacology at the University of California, Los Angeles, School of Medicine.

Ignarro’s research helped solve a mystery first uncovered in the late 1970s by American pharmacologist Robert F. Furchgott. Furchgott noted that blood vessels would expand, or dilate, only if a specific cellular layer surrounding the vessels—the endothelium—was intact. He proposed that cells in the endothelium released a chemical factor that caused smooth muscle cells around the vessel to relax, with the result that the vessel would dilate and blood flow would increase. Ignarro set out to identify this agent, which Furchgott had named endothelium-derived relaxing factor (EDRF).

Ignarro’s experiments led him to suspect that EDRF might be the gas NO. The prospect seemed unlikely because at the time NO was known primarily as an air pollutant. Ignarro pressed on with his research, however, and at a meeting of biomedical scientists in 1986, he officially proposed his theory that EDRF was NO. Furchgott, who had independently pursued the same theory, presented the same proposal at the meeting. Subsequent research supported their conclusion.

In the years following Ignarro and Furchgott’s discovery that EDRF and NO were the same substance, interest in NO virtually exploded. Based on the increasing knowledge of NO and its actions, scientists are pursuing new therapies for heart disease, cancer, septic shock, and other diseases. Even the celebrated anti-impotence drug Viagra owes a debt to Ignarro’s work. Viagra increases the blood flow in the penis, helping to produce an erection.

In 1998 Ignarro’s discoveries were honored with the Nobel Prize in physiology or medicine. He shared the prize with Furchgott and the American pharmacologist Ferid Murad, who had also achieved insights into NO’s cardiovascular function. Other honors received by Ignarro include the Merck Research Award in 1974 and the Lilly Research Award in 1978.