Perivenous localisation of Na‐dependent glutamate transport in perfused rat liver

Abstract

Periportal and perivenous hepatocytes differ in their metabolism of blood glutamate (Glu). Uncertainty about the mechanisms of Glu blood-liver exchange led us to characterise, by paired-tracer dilution, a sodium-dependent dicarboxylate transporter (resembling system X⁻ag) in sinusoidal membranes of perfused rat liver (V _max = 0.18 μmol Glu/g per min, K _m = 0.29 mM Glu). Tracer Glu transport was depressed 65% after necrosis of perivenous hepatocytes by acute CCl₄ treatment, indicating that X⁻ag transporter activity is located mainly in these cells, the sites of glutamine (Gln) synthesis from glutamate and ammonia. Modulation of Glu transport may influence the extent of hepatic Gln release.