Aim To investigate the protective effects and mechanisms of alendronate on vascular calcification in calcitoroil-induced rats with subtotal nephrectomy. Methods 30 SD rats were divided randomly into sham operation group;calcification group;alendronate group.Subtotal nephrectomy was performed by excision of two thirds of the left kidney followed by right nephrectomy 1 week later.Sham operation was performed by segregation of renal fascia without nephrectomy.After operation,all animals were treated with the high calcium(4%) and high phosphate(1.8%) diet.Meanwhile,all animals were intragastric administrated with calcitriol [1 μg/(kg·d)].Additionally,alendronate group rats were intraperitoneal injected with alendronate [0.25 mg/(kg·d)].4 weeks later,all rats were sacrificed by bleeding.For histological analysis of calcium accumulation,the beginning 1 cm of the abdominal aorta sections were removed and fixed in formalin,sectioned and histological stained(H&E and Von Kossa),and studied by microscope.For measurement of calcium content of the vessel wall,the abdominal aorta section beginning 1 cm and ending at femoral bifurcation were placed to different 2ml epitubes and 1 ml 150 mmol/L HCl was added to each tube.Each tube was closed securely and mixed end over end for 24 h.Calcium levels in the acid extract of tissues were determined by automatic biochemistry detection equipment.Serum concentration of osteocalcin was determined using an enzyme linked immunosorbent assay(ELISE). Results Extensive calcification was witnessed on the aortic tunica media of the calcification group rats,but less calcification in the alendronate group,and no calcification in the sham operation group.Calcium content of the vessel wall was significantly lower in alendronate group than those in calcification group(18.82±11.07 μmol/g vs 113.67±33.32 μmol/g,p<0.001),and there was no significant difference between alendronate group and sham operation group(18.82±11.07 μmol/g vs 6.67±2.82 μmol/g,p>0.05).Serum concentration of osteocalcin was significantly higher in alendronate group than those in calcification group(1.71±1.53 mmol/L vs 0.80±0.15 mmol/L,p<0.05),and sham operation group(1.71±1.53 mmol/L vs 0.74±0.38 mmol/L,p<0.05). Conclusion Injecting alendronate can inhibit vascular calcification in calcitoroil-induced rats with subtotal nephrectomy.