COMPARISON OF RELATIVE CHANGES IN PHOSPHATIC METABOLITES AND PHOSPHOLIPIDS AFTER IRRADIATION

Measurements of phosphatic metabolites and phospholipids using P-31 NM R spectroscopy were performed on tumor extracts at specific times befo re and after a priming dose of radiation at 32 or 65 Gy. At both doses , statistically significant increases in the high-energy phosphates PC r and ATP, relative to their primary hydrolysis product Pi, were detec ted at 24 h after irradiation. These spectral changes are consistent w ith an increased capacity for aerobic metabolism and oxidative phospho rylation. The changes coincide with a significant reduction in the hyp oxic cell fraction and 50% tumor control dose measurements reported pr eviously for the same tumor model. A significant increase in the ratio of phosphorylethanolamine to phosphorylcholine was also detected at 2 4 h, The ratio of ethanolamine-containing to choline-containing phosph olipids increased significantly between 48 and 96 h. The spectral chan ges measured in this study coincide with the changes in the hypoxic st ate of the tumor after irradiation and are consistent with spectral me asurements performed in vivo. The high-resolution spectroscopic data a lso identify specific metabolites contributing to spectral changes mea sured in vivo. (C) 1995 by Radiation Research Society