Characterisation of glutamine uptake in rat liver mitochondria

Glutamine is taken up by rat liver mitochondria in an electroneutral manner with a Km of 3.3 mM and a Vmax of 33 nmol x min-1 x mg-1 at 10 degrees C. The uptake is driven by the mitochondrial pH/cytosolic pH difference in isolated mitochondria, as well as in the intact rat liver. The rate of uptake is stimulated at a more alkaline matrix pH due to a stimulation of mitochondrial glutaminase. Our data confirm the notion that glutamine metabolism is regulated by pH, not only at the site of its metabolism but also through regulation of its transport systems.