Myocardial electrolytes in hypobaric hypoxia

Male, white rats (Holtzmann) were exposed to 7,200 m in a barometric chamber for six hours a day for three weeks. Control rats were kept at a sea level altitude of 200 m in Peoria, Illinois. At the end of the exposure period the rats were guillotined and their hearts removed. Approximately equal size strips were cut out of the right ventricles (RV), septa (S) and left ventricles (LV) and weighed on a Mettler balance. All heart pieces were dried overnight in a 40°C oven and reweighed following cooling. They were digested in concentrated nitric acid, diluted with distilled water; and sodium, potassium, calcium and magnesium were determined by atomic absorption spectrophotometry. RV and S muscle from the high altitude rats (HA) had a significantly higher water content. RV muscle from HA rats contained significantly more Na⁺, K⁺ and Ca⁺⁺ and less Mg⁺⁺ than sea level controls (SL). LV muscle from HA animals contained significantly less Na⁺ than SL controls. Within the HA hearts, the RV contained sïgnificantly more Na⁺, K⁺ and Ca⁺⁺ and significantly less Mg⁺⁺ than the S or LV. Evidence indicates that chronic high altitude exposure results in significant alterations in electrolyte distribution throughout the heart.Presented at the Seventh International Biometeorological Congress, 17–23 August 1975, College Park, Maryland, U.S.A.