Changes in potassium content of erythrocytes during exercise in man

Factors affecting erythrocyte K+ content and plasma electrolytes during light exercise were examined in 8 normal subjects and 27 patients with chronic obstructive lung disease. The patients were classified into bronchitis, emphysema and intermediate groups. Arterial blood was obtained during rest, after 2, 5, and 7 min. of exercise on a bicycle ergometer (30 km/h without mechanical brake), and at 10 and 20 min. during recovery for analysis of PO2, PCO2, plasma H+, Na+, K+, and Cl(-), erythrocyte K+ content and whole blood lactate. Plasma H+ increased significantly in all subjects after 2 min. of exercise and PCO2 rose in normal, bronchitis, and emphysema groups during exercise, whereas PO2 did not change significantly. Plasma K+ rose promptly after the beginning of exercise and remained at high values during exercise. The rapid rise in PCO2 was associated with a significant decrease of calculated erythrocyte K+ in patients with chronic bronchitis. Although changes in plasma H+ were dependent on both PCO2 and lactate, erythrocyte K+ changes were significantly related only to changes in PCO2. These results indicate that the decrease in erythrocyte K+ is mainly controlled by changes in arterial PCO2 during light exercise in patients with chronic bronchitis.