Induction of hepatic system y +-mediated L-arginine transport by prostaglandin E 2

Abstract

The in vivo effects of prostaglandin E 2 (PGE 2) 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 PGE 2, and HPMVs were prepared by Percoll density gradient centrifugation at varying time points after PGE 2 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 PGE 2 administration, at which time it reached peak effect. By 4 hours after PGE 2 treatment, arginine uptake had returned to control levels. Nonsaturable uptake (diffusion) was unaltered by PGE 2 treatment. Kinetic analysis showed a two-fold increase in the V max for system y + with no change in the K m, consistent with an increase in the number of functional y + carriers in the plasma membrane. These data indicate that PGE 2 stimulates hepatic arginine transport in vivo and suggest that prostaglandins play an important role in regulating arginine availability to the liver during critical illness.