J. Biol. Chem., Vol. 262, Issue 6, 2604-2607, 02, 1987
Compartmentation of 14CO2 in the perfused rat liver
C Marsolais, S Huot, F David, M Garneau and H Brunengraber
The specific activity of the mitochondrial CO2 + bicarbonate system has
been measured in perfused livers using the specific activities of urea and
acetoacetate derived from 2-ketoisocaproate catabolism. Label was supplied
either as NaH14CO3, 2-keto[1-14C]isocaproate, [1-14C]pyruvate,
[1-14C]glutamine, or [14C]formate. With labeled bicarbonate, pyruvate, or
2-ketoisocaproate, the specific activities of effluent bicarbonate, urea,
and acetoacetate were equal (acetoacetate was labeled only on C- 1). In the
presence of [14C]formate, the specific activity of acetoacetate was double
that of urea. Acetazolamide (0.2 mM), an inhibitor of carbonic anhydrase,
decreased the specific activities of urea and acetoacetate labeled from
NaH14CO3 and increased the specific activities of urea and acetoacetate
labeled from the other tracers. We conclude that: acetoacetate derived from
2-ketoisocaproate is, like urea, an index of the specific activity of
mitochondrial CO2 in liver, carbonic anhydrase activity equalizes the
specific activities of the CO2 + bicarbonate system on both sides of the
mitochondrial membrane, and a fraction of [14C] formate-derived 14CO2
appears to be generated in a mitochondrial compartment, in the close
vicinity of methylcrotonyl- CoA carboxylase.
CiteULike 
Complore 
Connotea 
Del.icio.us 
Digg 
Reddit 
Technorati What's this?
