CO 2 Permeability of Rat Hepatocytes and Relation of CO 2 Permeability to CO 2 Production

BACKGROUND/AIMS:It has been described that cells in culture with very low oxidative metabolism possess a low CO2 membrane permeability, PCO2, of ∼ 0.01 cm/s. On the other hand, cardiomyocytes and mitochondria with extremely high rates of O2 consumption exhibit very high CO2 membrane permeabilities of 0.1 and 0.3 cm/s, repectively. To ascertain that this represents a systematic relationship, we determine here PCO2 of hepatocytes, which exhibit an intermediate rate of O2 consumption. METHODS:We isolated intact hepatocytes with vitalities of ∼ 70% from rat liver and measured their CO2 permeability by the previously published mass spectrometric 18O exchange technique. RESULTS:We find a PCO2 of hepatocytes of 0.03 cm/s in the presence of FC5-208A and verapamil. FC5-208A was necessary to inhibt extracellular carbonic anhydrase, and verapamil was necessary to inhibit intracellular uptake of FC5-208A by the organic cation transporter OCT1 of hepatocytes. CONCLUSION:Rat hepatocytes with their intermediate rate of oxygen consumption also possess an intermediate CO2 permeability. From pairs of data for five types of cells/organelles, we find an excellent positive linear correlation between PCO2 and metabolic rate, suggesting an adaptation of PCO2 to the rate of O2 consumption.