Induction of hepatic system y(+)-mediated L-arginine transport by prostaglandin E2

The in vivo effects of prostaglandin E2 (PGE2) on L-arginine transport in rat liver were studied using hepatocyte plasma membrane vesicles (HPMVs). Adult rats were treated with a single intraperitoneal injection of PGE2, and HPMVs were prepared by Percoll density gradient centrifugation at varying time points after PGE2 administration. The activity of the sodium (Na+)-independent amino acid transport system y+ (arginine) was evaluated by uptake of tritium-labeled L-arginine using a rapid mixing/filtration technique. Arginine uptake was Na(+)-independent and consisted of saturable and nonsaturable components. Saturable arginine transport was increased 50% compared with controls 1 hour after PGE2 administration, at which time it reached peak effect. By 4 hours after PGE2 treatment, arginine uptake had returned to control levels. Nonsaturable uptake (diffusion) was unaltered by PGE2 treatment. Kinetic analysis showed a two-fold increase in the Vmax for system y+ with no change in the Km, consistent with an increase in the number of functional y+ carriers in the plasma membrane. These data indicate that PGE2 stimulates hepatic arginine transport in vivo and suggest that prostaglandins play an important role in regulating arginine availability to the liver during critical illness.