Biochemical metabolic changes assessed by 31P magnetic resonance spectroscopy after radiation-induced hepatic injury in rabbits.

AIM

To compare the features of biochemical metabolic changes detected by hepatic phosphorus-31 magnetic resonance spectroscopy ((31)P MRS) with the liver damage score (LDS) and pathologic changes in rabbits and to investigate the diagnostic value of (31)P MRS in acute hepatic radiation injury.

METHODS

A total of 30 rabbits received different radiation doses (ranging 5-20 Gy) to establish acute hepatic injury models. Blood biochemical tests, (31)P MRS and pathological examinations were carried out 24 h after irradiation. The degree of injury was evaluated according to LDS and pathology. Ten healthy rabbits served as controls. The MR examination was performed on a 1.5 T imager using a (1)H/(31)P surface coil by the 2D chemical shift imaging technique. The relative quantities of phosphomonoesters (PME), phosphodiesters (PDE), inorganic phosphate (Pi) and adenosine triphosphate (ATP) were measured. The data were statistically analyzed.

RESULTS

(1) Relative quantification of phosphorus metabolites: (a) ATP: there were significant differences (P < 0.05) (LDS-groups: control group vs mild group vs moderate group vs severe group, 1.83 +/- 0.33 vs 1.55 +/- 0.24 vs 1.27 +/- 0.09 vs 0.98 +/- 0.18; pathological groups: control group vs mild group vs moderate group vs severe group, 1.83 +/- 0.33 vs 1.58 +/- 0.25 vs 1.32 +/- 0.07 vs 1.02 +/- 0.18) of ATP relative quantification among control group, mild injured group, moderate injured group, and severe injured group according to both LDS grading and pathological grading, respectively, and it decreased progressively with the increased degree of injury (r = -0.723, P = 0.000). (b) PME and Pi; the relative quantification of PME and Pi decreased significantly in the severe injured group, and the difference between the control group and severe injured group was significant (P < 0.05) (PME: LDS-control group vs LDS-severe group, 0.86 +/- 0.23 vs 0.58 +/- 0.22, P = 0.031; pathological control group vs pathological severe group, 0.86 +/- 0.23 vs 0.60 +/- 0.21, P = 0.037; Pi: LDS-control group vs LDS-severe group, 0.74 +/- 0.18 vs 0.43 +/- 0.14, P = 0.013; pathological control group vs pathological severe group, 0.74 +/- 0.18 vs 0.43 +/- 0.14, P = 0.005) according to LDS grading and pathological grading, respectively. (c) PDE; there were no significant differences among groups according to LDS grading, and no significant differences between the control group and experimental groups according to pathological grading. (2) The ratio of relative quantification of phosphorus metabolites: significant differences (P < 0.05) (LDS-moderate group and LDS-severe group vs LDS-control group and LDS-mild group, 1.94 +/- 0.50 and 1.96 +/- 0.72 vs 1.43 +/- 0.31 and 1.40 +/- 0.38) were only found in PDE/ATP between the moderate injured group, the severe injured group and the control group, the mild injured group. No significant difference was found in other ratios of relative quantification of phosphorus metabolites.

CONCLUSION

(31)P MRS is a useful method to evaluate early acute hepatic radiation injury. The relative quantification of hepatic ATP levels, which can reflect the pathological severity of acute hepatic radiation injury, is correlated with LDS.