Effects of oxalate-degrading enzyme on the calcium oxalate kidney stones formation in intestinal hy-peroxaluria rats

Objective To observe the effects of oxalate-degrading enzyme on the formation of calcium oxalate kidney stones in intestinal hyperoxaluria rats. Methods From May to June, 2014, 8 healthy rats were selected as the negative control group named Group A. Intestinal hyperoxaluria rats were randomly divided into three groups (n=8): positive control group (Group B), low-dose enzyme gavage group (Group C) and high-dose enzyme gavage group (Group D). Group A were treated with normal saline by gavage (3 ml/d). Group B were treated with 4% ammonium oxalate solution by gavage (3 ml/d). Group C and Group D were treated with 20 U/d or 40 U/d enzyme on the basis of Group B. The intervention lasted for 4 weeks. The oxalate concentrations of 24 hours urine in each group were detected in 0, 7th, 14th, 21th, 28th day. The renal function, the serum and urine Ca2+ in each group were measured in 0 and 28th day. In 28th day, the kidneys of rats in Group A, B, D were examined by spectral CT. The kidneys of 4 groups were examined microscopically for possible calcium oxalate crystals. Results In 0 day, the urinary oxalate concentrations of Group A, B, C and D were (0.61±0.06), (1.58±0.15), (1.59±0.10) and (1.64±0.20) mmol/L. There were no significant differences among B, C and D(P>0.05). Compared with A, the urinary oxalate concentrations of B, C and D were significantly higher (P<0.001). After the enzyme gavage, the urinary oxalate concentrations of Group C and D were significantly decreased, and Group D decreased more significantly. In 28th day, the urinary oxalate concentrations of Group A, B, C and D were (0.61±0.11), (1.64±0.12), (1.17±0.12) and (0.87±0.11) mmol/L. After statistical analysis, the urinary oxalate concentration of Group C and D were significantly lower than Group B (P<0.01), and Group D decreased more significantly than that in Group C (P<0.01). The CT post-processing workstation data analysis suggested that the average CT value of Group B were significantly higher than D (P<0.01), and both of the two groups were higher than Group A (P<0.01); The differences were more obvious in conditions of low-kilovolt. Renal tubular calcium oxalate crystal deposition were seen the most in Group B, less in Group C and lowest in Group D. Whereas, there was no crystallization in Group A. Conclusion Oxalate-degrading enzymes could inhibit the formation of calcium oxalate kidney stones in intestinal hyperoxaluria rats. Key words: Kidney calculi; Oxalate-degrading enzymes; Hyperoxaluria; Calcium oxalate stones; Rats