Our red blood cells are packed with hemoglobin, which ferries oxygen from the lungs out to the body, where it picks up carbon dioxide and carries it back to the lungs to be exhaled. It’s a marvelous, well-known cycle. Yet last March researchers at Duke University Medical Center reported the discovery of something fundamentally new about the role of hemoglobin--a second chemical cycle that aids oxygen delivery.
The cycle involves nitric oxide (NO), which blood vessels secrete to dilate themselves. Like oxygen, NO can bind to the iron atom in hemoglobin--which had led some researchers to wonder why hemoglobin doesn’t sweep all the NO out of the bloodstream, constrict blood vessels, and send blood pressure through the roof. But cardiologist Jonathan Stamler and biochemist Joseph Bonaventura discovered that hemoglobin picks up NO not just in the blood but also in the lungs--where it’s produced in a chemically different form that ...
