Nitric Acid Found to Have Key Role in Respiration

Researchers have demonstrated that the chemical nitric oxide is an active regulatory molecule in the respiratory process that causes blood vessels to relax or constrict. They conclude that nitric oxide should be considered as the third major blood gas (along with oxygen and carbon dioxide) to be monitored in patients. Their findings were reported in the advance online issue of Nature Medicine on June 3, 2002.

In their studies, investigators tested the responses of the circulatory systems of human subjects in specialized chambers where the investigators could control atmospheric pressure and gas concentrations. They raised or lowered oxygen levels in the chambers and analyzed the response of the subjects' blood cells. This analysis showed that nitric oxide in the blood cells is an active regulatory molecule that causes the oxygen-carrying hemoglobin molecules in red blood cells to undergo subtle shape changes in response to varying concentrations of oxygen. Nitric oxide works by relaxing or contracting blood vessels. The findings explain why blood transfusions or drugs that boost red blood cell production don't work. They could also explain why there is a direct relationship between high red blood cell counts and stroke, heart attack, and hypertension.

"Instead of the total oxygen saturation of blood in the circulatory system, the key determinant of the efficiency of oxygen delivery is the flow of blood in the microvasculature,” said Jonathan Stamler, M.D., a senior member of the Duke research team. "Our data raise the possibility that the level of nitric oxide in the blood may provide physicians with a keen insight into the state of a patient's microvasculature.”




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