RESUMEN
Objective To investigate the effects of sericin pretreatment on the expression of extracellular matrix(ECM) associated protein in diabetic nephropathy(DN) rats' kidney.Methods Sixty six male SD rats were randomly divided into 3 groups(n=12):normal control group,DN model group and sericine pretreatment group.DN rats model in model group and sericine pretreatment group were established by intraperitoneally injection of streptozotocin(STZ).Blood glucose≥16.7 mmol/L was taken as the standard of successful modelization.The rats in sericine pretreatment group were lavaged with sericine(2.4 g·kg~(-1)·d~(-1)) for 35 days before injecting STZ.The enzymic method was used to measure the blood glucose.Type Ⅳ collagen(cⅣ)and laminin(LN)content in the serum were detected by ELBA.The expression of transforming growth factor-β_1,(TGF-β_1)and tissue inhibitors of maprix metalloproteinase-1(TMP-1) protein in the kidney was observed by immunohistochemical staining.The expression of Smad 3 protein in the kidney was detected by Western blot.Results Compared with normal control rats,the blood glucose,cⅣ and LN content in the serum,TGF-β_1,TIMP-1 and Smad 3 expression in the kidney of the model group rats increased obviously(P<0.01).The blood glucose,cⅣ and LN content in the serum,TGF-β_1,TMP-1 and Smad3 expression in the kidney of rats in sericine pretreatment group were significantly lower than those of the rats in model group(P<0.01).Conclusion Sericin pretreatment can inhibit the activation of TGF-β/Smad 3 signal pathway in the kidney of DN rats,and prevent the decrease of MMPs activity induced by up-regulation of TIMP-1.So sericin can prevent accumulation of ECM and glomerulosclerosis during DN,and has satisfactory apotropaic effects on the development of DN.