INDUCTION OF HEPATIC SYSTEM Y-MEDIATED L-ARGININE TRANSPORT BY PROSTAGLANDIN E(2)()

The in vivo effects of prostaglandin E(2) (PGE(2)) on L-arginine trans port in rat liver were studied using hepatocyte plasma membrane vesicl es (HPMVs). Adult rats were treated with a single intraperitoneal inje ction of PGE(2), and HPMVs were prepared by Percoll density gradient c entrifugation 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 u sing a rapid mixing/filtration technique. Arginine uptake was Naf-inde pendent and consisted of saturable and nonsaturable components. Satura ble arginine transport was increased 50% compared with controls 1 hour after PGE(2) administration, at which time it reached peak effect. By P hours after PGE(2) treatment, arginine uptake had returned to contr ol levels. Nonsaturable uptake (diffusion) was unaltered by PGE(2) tre atment. Kinetic analysis showed a twofold increase in the V-max for sy stem y(+) with no change in the K-m, consistent with an increase in th e number of functional y(+) carriers in the plasma membrane. These dat a indicate that PGE(2) stimulates hepatic arginine transport in vivo a nd suggest that prostaglandins play an important role in regulating ar ginine availability to the liver during critical illness.