Reassessment of 14CO2 compartmentation and of [14C]formate oxidation in rat liver |
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| Authors: | C Marsolais F Lafrenière F David S J Dodgson H Brunengraber |
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| Institution: | Department of Nutrition, University of Montreal, Quebec, Canada. |
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| Abstract: | Our previous report (Marsolais, C., Huot, S., David, F., Garneau, M., and Brunengraber, H. (1987) J. Biol. Chem. 262, 2604-2607) had concluded that a fraction of 14C]formate oxidation in liver occurs in the mitochondrion. This conclusion was based on the labeling patterns of urea and acetoacetate labeled via 14CO2 generated from 14C]formate and other 14C]substrates. We reassessed our interpretation in experiments conducted in (i) perifused mitochondria and (ii) isolated livers perfused with buffer containing 14C]formate, 14C]gluconolactone, 14CO2, or NaH13CO3, in the absence and presence of acetazolamide, an inhibitor of carbonic anhydrase. Our data show that the cytosolic pools of bicarbonate and CO2 are not in isotopic equilibrium when 14CO2 is generated in the cytosol or is supplied as NaH14CO3. We retract our earlier suggestion of a mitochondrial site of 14C]formate oxidation. |
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