In vivo 31P-nuclear magnetic resonance study of the response of a murine mammary tumor to different doses of gamma-radiation.

The response of the s.c. implanted murine mammary carcinoma NU-82 to 10 and 20 Gy of gamma-radiation was followed by in vivo 31P-nuclear magnetic resonance spectroscopy on 48 mice during a period of 2 days. During the first 8 h after a dose of 10 Gy, the ratio of ATP/inorganic phosphate increases to a value of 120 +/- 15% (SE) of the control value. This rise is followed by a decrease of the ratio to 74 +/- 12% after 47 h. However treatment with 20 Gy causes the ratio of ATP/Pi to decrease gradually to a level of 45 +/- 7% after 47 h. Histological investigations demonstrated that radiation-induced necrosis largely contributes to this phenomenon. During the time of observation irradiated tumors displayed no changes in size and intracellular pH. After treatment with 10 Gy as well as with 20 Gy, the phosphodiester resonance decreased in intensity. By 31P-nuclear magnetic resonance spectroscopy on extracts of the NU-82 tumor, two phosphodiesters were identified, glycerophosphocholine and glycerophosphoethanolamine.