Evidence for a hepatic transport system not responsive to glucagon or theophylline

Abstract

SummaryIn experiments designed to examine which transport systems are responsive to the adenine cyclase system, young rats received isotopically labeled, non-metabolizable amino acid analogs, selected for specificity to known transport systems. After allowing 38 hr for the amino acid to be distributed, glucagon or theophylline were injected intraperitoneally. Two amino acids typically reactive with a Na+-dependent transport system for neutral amino acids, and one with a system for cationic amino acids, showed sharply elevated hepatic levels, relative to the plasma. Levels for the first group also rose in the diaphragm. A model amino acid typically reactive with a Na+-insensitive transport system underwent no change in its distribution during 2 to 6 hr.