Reassessment of 14CO2 compartmentation and of [14C]formate oxidation in rat liver.
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.
Marsolais
C
C
Department of Nutrition, University of Montreal, Quebec, Canada.
Lafrenière
F
F
David
F
F
Dodgson
S J
SJ
Brunengraber
H
H
D000090:Acetoacetates / Q000378:metabolism; D000818:Animals; D001639:Bicarbonates / Q000378:metabolism; D002245:Carbon Dioxide / Q000378:metabolism*; D002250:Carbon Radioisotopes; D002956:Citrulline / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism; D005561:Formates / Q000378:metabolism*; D005947:Glucose / Q000378:metabolism; D008099:Liver / Q000378:metabolism*; D008930:Mitochondria, Liver / Q000378:metabolism; D010084:Oxidation-Reduction; D010477:Perfusion; D011865:Radioisotope Dilution Technique; D051381:Rats; D011919:Rats, Inbred Strains; D014508:Urea / Q000378:metabolism
D000090:Acetoacetates; D001639:Bicarbonates; D002250:Carbon Radioisotopes; D005561:Formates; D002245:Carbon Dioxide; D002956:Citrulline; D014508:Urea; D005947:Glucose