The findings of a recent study show that how red blood cells deliver oxygen from the lungs to tissue may reveal new insight into how the respiratory cycle works. The researchers showed that hemoglobin needs to carry nitric oxide to enable blood vessels to open and supply the oxygen to tissues. According to a Medical News Today report, the current convention describes the respiratory cycle as using blood to transport two gases (carbon dioxide and oxygen), but due to the study results, the research team argues that the respiratory cycle involves nitric oxide as a third gas.
The nitric oxide in this process controls the release of oxygen from red blood cells into the tissues that need it. In the study, the researchers used mice engineered to lack the ability to carry nitric oxide in their red blood vessels to show how nitric oxide controls the blood flow in small blood vessels inside tissue in the process “blood flow autoregulation.”
The researchers found mice could not oxygenate their muscle tissue; essentially, their blood flow autoregulation just did not work in the absence of nitric oxide, though their red blood cells were able to carry a full load of oxygen. They just could not unload it. The Medical News Today report notes that when the researchers induced slight oxygen deprivation (hypoxia) in the mice, the blood flow to their organs dropped sharply, triggering heart attacks and heart failure.
In normal mice, the lack of oxygen prompts a spike in blood flow so more oxygenated blood reaches cells and tissues, but this did not happen in the mice whose red blood cells lacked nitric oxide.
Jonathan Stamler, one of the researchers of the study, says that how the mice had red blood cells “by all traditional measures are completely normal in carrying oxygen and releasing it and then in picking up carbon dioxide, yet these animals cannot oxygenate their tissues. Lacking nitric oxide in red cells, oxygen deficiency could not induce vasodilation, which is essential for sustaining life as we know it.”
The results of the study also provide evidence that blood flow is not just under the control of blood vessels; red blood cells are involved as well.
Stamler concludes, “It’s not enough to increase to oxygen content of blood by transfusion; if the nitric oxide mechanism is shot, oxygen cannot make it to its destination. We know that blood in a blood bank is deficient in nitric oxide, so infusing that blood may cause plugging of blood vessels in tissues, making things worse.”
Source: Medical News Today