Effects Of Different Doses Of Calcitriol On Aortic Calcification In Rats With Chronic Renal Failure

Objectives To investigate the effects of different doses of calcitriol on aortic calcification in rats with chronic renal failure.Methods First of all,40 SD rats were randomly divided into Sham group(n=10)and model group(n=30).After anes-thesia,left kidney(1/3 of upper and lower levels)was removed in the model group,followed by right kidney resection 1 week later,with a total of 5/6 renal tissue removed.In the Sham group,the operation was performed in the same way,with only renal capsule separated without renal tissue resection.After 4 weeks postoperatively at feeding,extract the rat tail venous blood line if renal function tests are clearly building success.After the successful establishment of renal failure model,the model group was randomly divided into high phosphorus diet group(Nx-Hp,n=10),high phosphorus diet and calcitriol low-dose group(Nx-Hp+L,n=10),high phosphorus diet and calcitriol high-dose group(Nx-Hp+H,n=10).Sham group was given normal diet feeding,Nx-Hp group,Nx-Hp+L group and Nx-Hp+H group were fed with the same amount of high-phosphorus diet(containing 1.2% phosphorus and 1.6% calcium),and the Nx-Hp+L group was gavaged 0.10μg/kg/d calcitriol,the Nx-Hp+H group was gavaged 1.0μg/kg/d calcitriol.After 10 weeks of drug intervention,blood from the inferior vena cava was collected to detect the levels of blood calcium and blood phosphorus,the head was decapitated and sacrificed.All the thoracic aorta of rats were collected and the upper 1/3 of the aorta was stored in liquid nitrogen at low temperature for calcium content detection.The third segment was stored in a refrigerator at-80 ℃ for fluorescence quantitative PCR detection of Bone morphogenetic protein2(BMP2),Smad1 and runtrealted tran-scripition factor2(Runx2).Von Kossa staining was used to observe the degree of vascular calcification in the lower third of the segment,and the expression levels of BMP2,Smad1 and Runx2 protein were measured by immunohis-tochemistry.The renal tissue was fixed with 10% neutral formalin buffer,the glomeruli,tubules and interstitium were observed under microscope.All samples were collected immedi-ately after the rats died.Results 1 Renal function changes(4 weeks after surgery):compared with Sham group,blood urea nitrogen and creatinine levels in model group were significantly increased,with statistical significance(P<0.05).2 Renal pathological changes of rats in each group:there was no significant change in renal pathology in sham group,the renal pathology in Nx-Hp+L group was slightly lighter than that in Nx-Hp group,with glomerulosclerosis,dilatation of some renal tubules and a small amount of fibrosis in renal interstitium,the pathological changes in Nx-Hp group and Nx-Hp+H group were more severe,with glomerulosclerosis,disordered renal tubular structure,dilatation in many places,infiltration of inflammatory cells and fibrous hyperplasia in renal interstitium,and Nx-Hp+H group was more serious than Nx-Hp group.3 Comparison results of serum calcium and phosphorus concentrations in each group showed that(drug intervention for 10 weeks):the serum calcium concentration of Nx-Hp group was lower than that of Nx-Hp+Lgroup,Nx-Hp+H group and Sham group(P<0.05),and the serum calcium concentra-tion of Nx-Hp+H group was the highest(P<0.05),the serum calcium concentration of Nx-Hp+L group was not significantly different from that of Sham group(P>0.05);The blood phosphorus concentration in Sham group was significantly lower than that in the other three groups(P<0.05),and the blood phosphorus concentration in Nx-Hp+H group was the highest(P<0.05),the blood phosphorus concentration in Nx-Hp+L group was significantly lower than that in Nx-Hp group(P<0.05).4 Comparison of Von Kossa staining results of thoracic aorta vessels in each group:compared with the Sham group,black calcium salt deposits were observed in the other three groups,spotty and patch-like calcium deposits were observed in the rats of Nx-Hp+L group,severe calcium deposits were observed in the rats of Nx-Hp+H group and many linear black deposits were observed,the calcification degree of Nx-Hp+H group was significantly worse than that of the Nx-Hp group.5 Comparison results of calcium content in thoracic aorta of rats in each group showed as follows:the vascular calcium content of Nx-Hp group,Nx-Hp+H group and Nx-Hp+L group was higher than that of Sham group(P<0.05),and the vascular calcium content of Nx-Hp+H group was the highest(P<0.05),and the vascular calcium content of Nx-Hp+L group was lower than that of Nx-Hp group(P<0.05).6 Comparison of Average Optical Density(AOD)value of BMP2,Smad1 and Runx2 in thoracic aorta of rats in each group:compared with Sham group,AOD values of BMP2,Smad1 and Runx2 in the other three groups were significantly increased(P<0.05),and AOD value of Nx-Hp+H group was the highest(P<0.05),AOD value of Nx-Hp+L group was lower than that of Nx-Hp group(P<0.05).7 Comparison of PCR results of BMP2,Smad1 and Runx2 in thoracic aorta of rats in each group showed that:compared with Sham group,the m RNA relative expression levels of BMP2,Smad1 and Runx2 in Nx-Hp+L group,Nx-Hp+H group and Nx-HP group were increased(P<0.05),and the m RNA relative expression levels of BMP2,Smad1 and Runx2 in Nx-Hp+H group were the highest(P<0.05),the m RNA relative expression levels of BMP2,Smad1 and Runx2 in Nx-Hp+L group were lower than those in Nx-Hp group(P<0.05).Conclusions Different doses of calcitriol have different effects on aortic calcification in rats with chronic renal failure.Low dose of calcitriol can inhibit the occurrence of vascular calcification,while high dose of calcitriol can promote the occurrence of vascular calcification,the mechanism may be that low dose of calcitriol inhibits the expression of BMP2/Smad1/Runx2 signaling pathway,while high dose of calcitriol activates the expression of this pathway.Figure 3;Table 7;Reference 88...