A range of variation in percent of oxygen saturation of arterial hemoglobin
(SaO(2)) among healthy individuals at a given high altitude indicates diff
erences in physiological hypoxemia despite uniform ambient hypoxic stress.
In populations native to the Tibetan plateau, a significant portion of the
variance is attributable to additive genetic factors, and there is a major
gene influencing SaO(2). To determine whether there is genetic variance in
other high-altitude populations, we designed a study to test the hypothesis
that additive genetic factors contribute to phenotypic variation in SaO(2)
among Aymara natives of the Andean plateau, a population geographically di
stant from the Tibetan plateau and with a long, separate history of high-al
titude residence. The average SaO(2) of 381 Aymara at 3,900-4,000 m was 92
+/- 0.15% (SEM) with a range of 84-99%. The average was 2.6% higher than th
e average SaO(2) of a sample of Tibetans at 3,800-4,065 m measured with the
same techniques. Quantitative genetic analyses of the Aymara sample detect
ed no significant variance attributable to genetic factors. The presence of
genetic variance in SaO(2) in the Tibetan sample and its absence in the Ay
mara sample indicate there is potential for natural selection on this trait
in the Tibetan but not the Aymara population. (C) 1999 Wiley-Liss, Inc.