| Objective Disorders of mineral and bone metabolism are common complications of chronic kidney disease (CKD).With the progression of chronic kidney disease, patients will suffer from the abnormalities of calcium, phosphorus, PTH, renal osteodystrophy and vascular calcification, called Chronic Kidney Disease-Mineral Bone Disorder (CKD-MBD), and elevates the mortality of the patients. In our study, To observe bone morphology changes in chronic renal failure rats that were fed different levels of dietary phosphorus for long term.Methods twenty four male S-D rats were divided into high-phosphorus diet group (CRF-HP group), low phosphorus diet group (CRF-LP group), model group (CRF group), sham operation group (sham group) (n=6).5/6 nephrectomy models of chronic renal failure were prepared for CRF-HP group, CRF-LP group and CRF group, the sham group was prepared as same as other groups except nephrectomy. After 4 weeks, the first 3 groups were received high phosphorus diet (P 1.2%, calcium 1.6%), low phosphorus diet (P 0.2%, calcium 0.5%), normal phosphorus diet (P 0.9%, 1.2% calcium). Sham group received normal phosphorus diet, too. Every 6 weeks, the blood and urine was collected. After the serum creatinine levels were tested at week 24, the rats were sacrificed, and their femurs were removed, fixed-embedded, and examined with Giemsa, Von Kossa staining. Trabecular bone volume calculation (TBV), osteoblast index (OBI), the osteoclast index (OCI) and osteoid volume (OV/ TV) were measured, and the morphological changes of cortical bone were observed. By tetracycline double labeling technique, bone formation rate (MAR) was analyzed.Results The survival number in CRF- HP group, CRF-LP group, model group and Sham group were 6,3,5,6 respectively.At the 24 week, proteinuria of the CRF-HP group, CRF-LP group and CRF group was higher than Sham group (101.51±16.21 vs7.44±2.67, P<0.01; 62.66±27.58 vs7.44±2.67, P<0.01; 45.83±15.90 vs 7.44±2.67 P<0.05), proteinuria of CRF- HP group rats was higher than CRF group (P <0.05),there was no differce between CRF- HP group and CRF group(P>0.05). At the 6 week, the SCr of HP, LP and CRF groups were more than Sham group(114.0±38.4vs62.4±4.1,P<0.01; 118.1±25.0 vs62.4±4.1,P<0.01;109.0±17.3 vs62.4 ±4.1, P<0.01), HP, LP and CRF groups had no difference, showing that HP, LP and CRF groups rats were renal failure at the same level. And at 24 week, the SCr of HP, LP and CRF group rats were also at the same level, showing that different levels of phosphrus diet did not affect the renal function. The Ca of the four groups had no difference. Excretory rate of urinous calcium of LP lower than CRF group(7.6±2.39 vs12.8±3.56, P<0.05) at 12 week, and at 18 week excretory rate of urinous calcium of LP lower than other groups (9.0±3.16 vsl5.5±1.73, P<0.001; 9.3±3.20 vs15.5±1.73 P <0.01; 6.0±3.08 vs15.5±1.73 P<0.01). The Pi of LP group was higher than others at 12 week (2.47±0.17 vs2.70±0.26, P<0.01; 2.34±0.09 vs2.70±0.26 P<0.01; 2.44±0.18 vs2.70±0.26, P<0.05).The excretory rate of ruinous phosphate of HP were more other groups. They were still higher than LP after corrected by CCr (223.8±89.7 vs54.9±28.6, P<0.01; 622.1±330.7 vs174.5±87.6, P<0.01; 467.8±273.7 vs306.6±119.3, P<0.05; 522.3±287.5 vs143.0±103.8, P<0.05). At 12 and 18 weeks, The excretory rate of ruinous phosphate of HP corrected by CCr were also higher than CRF group (622.1±330.7 vs235.2±58.4, P<0.05; 467.8±273.7 vs147.5±37.5, P<0.05). In model group, TBV, OBI, OCI, OV/TV were significantly increased compared with those in sham group (20.2±6.3 vs14.4±5.2, P<0.05; 141.0±53.3 vs80.0±24.1, P<0.05; 9.4±3.0 vs4.5±1.3, P<0.01; 1.14±0.02 vs0.21±0.03, P<0.01), and so were MAR (2.1±0.4 vsl.4±0.8, P<0.01). These changes in high-dose HP group were even more evident than those in model group (all P<0.05), but the cortical bone porosity increased. TBV, OCI, MAR in LP rats were significantly lower than those in model group, but OV/TV increased. MAR in LP rats significantly lower than normal rats.Conclusion 24 weeks high-phosphorus diet has a significant effect on the excretory rate of ruinous phosphate; high-phosphorus diet increase the proteinuria of urimic rats, but has no effect on renal function, serum Ca and P; 24 weeks high-phosphorus diet in urimic rats can significantly increased bone turnover rate, increase cancellous bone, decrease cortical bone, low phosphorus diet can effectively correct the increased rate of bone turnover in urimic rats, reduce mineral apposition rate and cancellous bone volume. High-phosphorus diet fed 5/6 nephrectomy rats can make High Bone- Turnover Disease moldel, but low-phosphorus diet fed 5/6 nephrectomy rats are not High Bone- Turnover Disease moldel. |
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