Specific localization of α-ketoglutarate uptake to dog kidney and liver in vivo

Abstract

Net uptake of infused α-ketoglutarate (α-KG) occurs almost exclusively in dog kidney and liver; in contrast, lactate or pyruvate uptake occurs in most organs. The following observations support these conclusions: 1) in measurements of steady-state net renal and whole-body uptake of α-KG, lactate, and pyruvate, kidney takes up ≈50% of the total α-KG utilized as compared to lactate (≈15%) or pyruvate (≈17%); 2) liver and kidney extract more α-KG from blood than do the lower extremities, brain, intestine, or heart; 3) exclusion of either the kidneys or the liver, or both, from the circulation shows that these organs are the major determinants of the rate of α-KG clearance from blood. The virtual volume of α-KG distribution in the hepatectomized, nephrectomized dog is approximately that of extracellular fluid. The selective uptake of α-KG is compared to the membrane transport of p-aminohippurate (PAH) by these two organs. It is suggested that the general, and perhaps primary, function of the PAH transport system is to move specific metabolites to sites of dissimilation in liver and kidney.