The Role of Stimulated Amino Acid Transport in Promoting Glycogenesis in the Irradiated Rat

• Published in: Radiation research 1976-06, Vol.66 (3), p.597-608
• Main Authors: Kilberg, Michael S., Neuhaus, Otto W.
• Format: Article
• Language: English
• Subjects: Amino acids; Amino Acids - blood; Amino Acids - metabolism; Animals; Cesium Radioisotopes; Dosage; Enzymes; Gamma Rays; Gluconeogenesis; Glycogen; Irradiation; Liver; Liver - metabolism; Liver glycogen; Liver Glycogen - biosynthesis; Male; Radiation Injuries, Experimental - metabolism; Radiocarbon; Rats; Whole body irradiation
• ISSN: 0033-7587; 1938-5404
• DOI: 10.2307/3574463

Whole-body irradiation of rats stimulates an amino acid transport system in the liver. Another phenomenon observed after exposure to ionizing radiations is the accumulation of hepatic glycogen. The data presented here relate the increased hepatic uptake of amino acids to glycogenesis. Male rats were exposed to two doses of γ rays, 2500 and 1500 R. Following exposure to 2500 R, the hepatic free amino acids were elevated during the first 48 hr accompanied by a decline in serum levels. At 72 hr the hepatic amino acids diminished to the control levels while the serum increased abruptly. By contrast, 72 hr after exposure to 1500 R the serum amino acid levels increased only 27% and the hepatic amino acid values increased 52%. These results are explained on the basis of the changes in AIB transport previously reported. The incorporation of 14 C from labeled L-alanine into hepatic glycogen was maximal 48 hr postexposure to 2500 R but declined to below control values at 72 hr. On the other hand, exposure to 1500 R resulted in maximal incorporation of 14 C at both 48 and 72 hr. We propose that transport of amino acids into liver cells is stimulated by the elevated blood levels of amino acids released from the degradation of protein. The transport increases the levels of hepatic free amino acids, and therefore, is a key factor in regulating postirradiation glycogenesis.