| Objective Renal osteodystrophy is a disease of bone metabolism disturbances with chronic renal failure (CRF). It is necessary to take attention on changes of bone metabolism and have an early management. Radiation treatment for abdomen tumour is a common cause for injury to kidney. The aim of this study was to invest the bone metabolism responded to renal radiation injury, the pathological changes and its mechanism. The prevention and management of kidney-nourishing herbs to the bone lesion induced by renal radiation injury was also explored.Methods The model was established by kidney exposed to 15 Gy of Cs137 γ-rays. An assay of 25-hydroxyvitamin D3-1 alpha-hydroxylase activities was developed using rat kidney homogenates incubated with 25-hydroxyvitamin D3. Enzymatic activity was assessed by utilizing RIA and measuring on HPLC the formation of 1 alpha,25(OH)2D3. The changes of bone metabolism responded to renal radiation injury including renal organ pathology, bone volume, bone histomorphometry and biomechanical properties and biochemical markers were observed, and its mechanisms was explored. Kidney-nourishing herbs active components extracted by vegetable chemistry method were given to the rats one week after radiation for 90 days. The preventive and therapeutic effects of kidney-nourishing herbs on bone metabolism disturbances induced by renal radiation injury and the pharmacological effects on improving renal function and 1 alpha-hydroxylase activity were observed. The response to kidney-nourishing herbs or the drug serum was studied in osteoblast cultured in vitro. Osteoblast proliferation ratio, ALP activity and mineralizing ability were assayed. Results After 3 months of kidney radiation by 15 Gy of Cs137 γ-rays, the changes with kidney shrank, Bowman's capsules straitened or disappeared, glomerular swelled, some epithelia denaturalized or died were observed. Mitochondria tumefied and the cristae shortened, lessened and disordered. Urine β2-MP rose evidently. It was lowered significantly the renal 25-OH-D-1α-hydroxylaseactivity and its mRNA expression. The dry and ash weight, BMD of femur and lumbar were significantly reduced, volume and width of bone trabecula were distinctly decreased and the space increased in model group. The Pyd / Cr increased and ALP decreased as well. However, in kidney-nourishing herbs group compared with renal radiation group, morphologic changes improved with a lower urine β2-MP, higher renal 1α-hydroxylase activity and its mRNA expression and better recovery in bone volume, bone histomorphometry and biomechanical properties. It was evident the enhancement of kidney-nourishing herbs and the drug serum on proliferation ratio, ALP activity, mineralizing function and exprosion of OPG mRNA in osteoblast cultured in vitro while expression of RANKL mRNA down-regulated. Conclusions (1) 15 Gy of Cs137 γ-rays resulted in evident changes of renal patholoy and function. (2) Renal radiation injury can induce bone metabolism disturbances with bone loss, bone histomorphometry and biomechanical properties lesions. (3) It was the main mechanism for bone metabolism disorder to decrease renal 1α-hydroxylase activity mRNA expression induced by renal radiation injury. (4) Kidney-nourishing herbs can improve disturbances of bone metabolism in rats induced by renal radiation injury. The mechanism may be that it can recover renal damage and improve renal 1α-hydroxylase activity. (5) Kidney-nourishing herbs has the effect on enhancing proliferation ratio, ALP activity and mineralizing nodules formation in osteoblast cultured in vitro.
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