Characterization of sodium-dependent amino acid transport activity during liver regeneration

✍ Scribed by Fred C. Fowler; Robert K. Banks; Mark E. Mailliard

• Publisher: John Wiley and Sons
• Year: 1992
• Tongue: English
• Weight: 926 KB
• Volume: 16
• Category: Article
• ISSN: 0270-9139
• DOI: 10.1002/hep.1840160514

✦ Synopsis

Liver mgeneration occurs after removal of or damage to a portion of the liver; it leads to restoration of the original liver mass. The activities of three eodium-dependent amino acid transporterssystem A, e m N and ayetem ASC -were determined during a Baay period of liver regeneration in the rat. Seventypercent hepatectomy or laparotomy was performed in pairs of rats; these rats' livers were removed at different time points after surgery. Transport activity was determined through measurement of the Na'dependent uptake of tritiated amino acids by isolated hepatic plamna membrane vesicles. System A activity, as measured by the Na+-dependent uptake of 2-amhoiaobutyric acid, is increased in the reqgenerating liver 2 to 24 hr after surgery compared with that of controls. Kinetic analysis of 2-(methylamino)iaobutyric acid uptake showed a 100% inmase in the maximum velocity of eystem A tramport in the hepatectomized animals with no change in the Michaelis constant, suggding an increase in the number of syatem A transport proteins in the plasma membrane of regenerating liver. During liver regeneration, no changes were noted in the transport activities of aystem N and system ASC as measured by the uptake of glutamine and cyateine, reepectively, in the presence of 2-(methylamino)isobutyric acid. Our work suggests that aystem A performs a unique role in the secondary active transport of its substrate neutral amino acids to meet the metabolic demands of regenerating liver.