Early radiation effects in highly apoptotic murine lymphoma xenografts monitored by 31P magnetic resonance spectroscopy.
OBJECTIVE
Phosphorus-31 magnetic resonance spectra (31P-MRS) were obtained from highly apoptotic murine lymphoma xenografts before and up to 24 hr following graded doses of radiation ranging from 2 to 30 Gy. Radiation-induced apoptosis was also estimated up to 24 hr by scoring apoptotic cells in tumor tissue.


METHODS
Highly apoptotic murine lymphoma cells, EL4, were subcutaneously transplanted into C57/BL mice. At 7 days after transplantation, radiation was given to the tumor with a single dose at 3, 10, and 30 Gy. The beta-ATP/Pi, PME/Pi, and beta-ATP/PME values were calculated from the peak area of each spectrum. Radiation-induced apoptosis was scored with counting apoptotic cells on hematoxylin and eosin stained specimens (% apoptosis).


RESULTS
The values of % apoptosis 4, 8, and 24 hr after radiation were 21.8, 19.6, and 4.6% at 3 Gy, 35.1, 25.6, and 14.8% at 10 Gy, 38.4, 38.0, and 30.6% at 30 Gy, respectively (cf. 4.4% in control). There was no correlation between early change in beta-ATP/Pi and % apoptosis at 4 hr after radiation when most of the apoptosis occurred. An early decrease in PME/Pi was observed at 4 hr after radiation dose at 30 Gy. For each dose, the values of beta-ATP/Pi 24 hr after radiation were inversely related to radiation dose.


CONCLUSIONS
The increase in beta-ATP/Pi observed by 31P-MRS was linked to the degree of histological recovery from radiation-induced apoptosis.
Department of Radiology and Radiation Oncology, Gunma University School of Medicine, Maebashi, Japan.
H
H
Sakurai
N
N
Mitsuhashi
O
O
Murata
Y
Y
Kitamoto
Y
Y
Saito
M
M
Hasegawa
T
T
Akimoto
T
T
Takahashi
S
S
Nasu
H
H
Niibe
D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D017209:Apoptosis / Q000528:radiation effects*; D008223:Lymphoma / Q000378:metabolism / Q000473:pathology / Q000532:radiotherapy*; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D010758:Phosphorus; D011829:Radiation Dosage; D013997:Time Factors; D014183:Transplantation, Heterologous; D014407:Tumor Cells, Cultured / Q000528:radiation effects
D010758:Phosphorus; D000255:Adenosine Triphosphate