GLUTAMINE UPTAKE BY ISOLATED RAT-BRAIN MITOCHONDRIA

The existence of a specific mechanism for glutamine transport is demonstrated by observation that brain mitochondria swell when incubated in iso-osmolar solutions of this neutral amino acid. There is no proton or ionophore requirement, but a metabolic energy supply increases the rate of swelling. Carrier mediation is strongly suggested by the observation that L-glutamine is transported more rapidly than its D-isomer. Transport is inhibited by ionic mercurials, but not by N-ethylmaleimide, which rules out any link between glutamine uptake and glutamate efflux. .alpha.-Ketoglutarate and glutamate are powerful inhibitors of glutamine transport. Interactions between the specific glutamine transport mechanism and the intramitochondrial phosphate-dependent glutaminase activity are discussed.