Elevated nitric oxide in blood is key to high altitude function fo...( CLEVELANDHow can some people live at...)

CLEVELANDHow can some people live at high altitudes and thrive while others struggle to obtain enough oxygen to function?

The answer for Tibetans who live at altitudes around 14,000 feet is increased nitric oxide (NO) levels. High levels of NO circulate in various forms in the blood and produce the physiological mechanisms that cause the increased blood flow that maintains oxygen delivery despite hypoxialow levels of oxygen in the ambient air and the bloodstream. Researchers from Case Western Reserve University and the Cleveland Clinic report that Tibetans have 10 times more NO and have more than double the forearm blood flow of low-altitude dwellers. The findings from a comparison of NO levels in the high and low altitude dwellers are reported in the article, Higher Blood Flow and Circulating NO Products Offset High-altitude Hypoxia among Tibetans, in the current Proceedings of the National Academy of Sciences (PNAS).

The low barometric pressure of high altitudes generally causes low arterial oxygen content among Tibetans, yet the researchers have found that Tibetans consume oxygen at normal rates.

We asked how that could be done, said Cynthia Beall, the S. Idell Pyle Professor of Anthropology at Case Western Reserve University. For two decades, Beall has been one of the worlds leading researchers in the studies of high altitude adaptation in different populations in Ethiopia, South America and Tibet.

Beall collected blood samples and blood flow readings from the forearms of 88 Tibetans during a 2002 research trip that was funded by the National Science Foundation. The blood flow data and blood samples were brought back to the United States where Serpil Erzurum, chair of pathobiology, Cleveland Clinic, and the papers lead author, analyzed the information. In Erzurums lab, Allison Janocha, a Case Western Reserve graduate, performed many of the technically challenging analyses.

For comparison, the scientists collected the same in
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