METHEMOGLOBIN AND ERYTHROCYTE REDUCING SYSTEMS IN HIGH-ALTITUDE NATIVES

The stress of chronic hypobaric hypoxia present at high altitudes induces a series of adaptive changes in the intermediate metabolism in erythrocytes of high-altitude natives. Aymaras of the high Andean Plateau have within erythrocytes: (a) increased activity of NADH2 (GAPH [glyceraldehyde-3-phosphate dehydrogenase]) generating stages, (b) decreased activity of NADH2 (LDH [lactate dehydrogenase]) consuming steps, (c) significantly increased methemoglobin content, and (d) a large increase in the level of reduced glutathione. These alterations occur also in persons of the same ethnic group residing at low altitude. There is only a moderate elevation of classic hematological parameters (erythrocyte count, Hb and hematocrit) in highland natives. The functional implications of these metabolic changes are discussed with respect to regulation of erythrocyte metabolism.