Transport of Na+ and HCO3– Out of Red Blood Cells Is Simultaneous with a Chloride Shift in Canine and Human Whole Blood exposed to Co2-Rich Gas

: To study the release of Na+ from erythrocytes, arterial whole blood obtained from anesthetized and heparinized dogs (n = 8), or human (n = 9) venous blood was aerated with a CO2-rich gas mixture (15% CO2, 25% O2, 60% N2) at a rate of 1 l/min. To examine possible mechanisms involved in the release of sodium ions into plasma, CO2-rich gas was also passed through whole blood in the presence of acetazolamide (n = 8), SITS (n = 8), or furosemide (n = 8). The changes in blood gas parameters, plasma protein concentration, hematocrit, and plasma sodium, chloride, and bicarbonate ion concentrations were examined. When CO2-rich gas was passed through treated and untreated canine or human whole blood, PCO2 and plasma sodium and bicarbonate contents per ml of blood increased, while pH and plasma chloride content per ml of whole blood decreased. After 0 to 5 min of CO2-rich gassing, the mean rates of change in plasma ion contents per ml of whole blood per min were related by the following equations: (1) delta MCI- = a (delta MNa+), (2) delta MHCO3- = b(delta MNa+), (3) delta MHCO3- approximately equal to delta MNa+ + delta MCl-, (4) b approximately equal to 1 + a. These results suggest that the release of Na+ and HCO3- from erythrocytes into plasma in canine and human whole blood occurred in a one-to-one ratio simultaneously with, and probably independently of, the well-known chloride shift during a period of 0 to 5 min after the start of CO2-rich gassing.