Anaerobic CO2 production by dog kidney in vitro

Abstract

Does dog kidney have the capacity to produce CO2 anaerobically? Such "extra CO2" production could account for the high renal RQ [respiratory quotient] observed in vivo. Of several anerobic decarboxylations which occur in kidney, we studies: a-ketoglutarate + oxaloacetate + ADP [adenosine diphosphate][forward arrow]malate + succinate + CO2 + ATP [adenosine triphosphate], which, like glycoly-sis, results in substrate level phosphorylation. Washed homogenates and slices from dog renal cortex and medulla were incubated anaero-bically with 2-33 mM [alpha] -KG and 33-42 mM OAA [oxaloacetate]: CO2 production ([mu]moles CO2/1OO mg dry wt./hr.) by cortical homogenates was 14. 6 [plus or minus] 1. 8 (mean [plus or minus] SE); medullary homogenates produced 1. 4 [plus or minus] 0.5. Cortical slices produced 17. 4[plus or minus]1.5; medullary slices yielded only 0. 6 [plus or minus] 1.3. Chemical balances in homogenates were consistent with the above reaction; in slices, other reactions also contribute to CO2 production. Cortical and medullary succinic-DH [reduced] and [alpha]-KG [alpha-ketoglutarate]-DH [reduced] activities were similar; medullary malic-DH activity was almost absent. The large potential for anaerobic CO2 production by cortex is consistent with the high renal RQ [respiratory quotient] and with a moiety of ATP production independent of renal QO2 [O2 production] or lactate production.