BOHR SHIFT BY LACTIC-ACID AND THE SUPPLY OF O2 TO SKELETAL-MUSCLE

Conditions simulating changes during physical exercise were induced in erythrocytes to determine the resulting Bohr effect. Lactic acid was added to red cell suspensions and whole blood with initial 25 and 60% S(O2), at 42 Torr P(CO2), and temperatures of 20 and 37-degrees-C. Changes in pH, P(O2) and S(O2) were measured. CO2 liberation from buffering lactic acid in the extracellular fluid and its diffusion into erythrocytes resulted in an exaggerated Bohr shift, if the gas could not escape from the liquid phase (closed system, 'muscle' conditions). P(O2) at constant S(O2) increased by up to 11.7%.mmol-1.L lactic acid. After reequilibration to initial P(CO2) values (open system, 'lung' conditions) the Bohr shift decreased (remaining P(O2) increase 0.7-1.4%.mmol-1.L) mainly caused by the reduced acidification. In addition, the Bohr coefficients (BC) under closed conditions were larger (-0.36 to -0.50) than after reequilibration (-0.20 to -0.38). This difference is attributed to a larger CO2BC than fixed acid BC. These effects might be enhanced in vivo by temperature differences between muscle and lung, lowered nonbicarbonate buffering of blood and counter-current blood flow in muscle.