Study On α-smooth Muscle Actin Expression In Kidney Of Diabetic Rats

Objective and background:Diabetic nephropathy (DN) is one of the most important microvascular complications of diabetes mellitus. So far ,there was no certain pathogenesis and effective therapeutic intervention of DN. DN is characterized by a complex accumulation of extracellular matrix proteins (ECM), resulting in diffuse glomerrular sclerosis and progressive tubulointerstitial fibrosis.Q -smooth muscle actin( a SMA)is one of the cytoskeletal proteins in vascular walls. Fewer a SMA are expressed in normal renal except vascular media Either in immuno or in non -immuno progressive renal injury, the activated mesangial cells and myofibroblasts can express a SMA .The appearance of a SMA seems to accompany expansion of ECM and finally lead to tubulointerstitial fibrosis with ultimate loss of renal function.In order to know whether the deposition of ECM is associated with the expression of a SMA ,we examind a SMA and the type IV collagen in the kidney of diabetic rats using immunohistochemistry.Research Design and Methods:Diabetes was induced in 35 Sprague-Dawley (SD) rats by a single intraperitoneal injection of streptozotocin (70mg/kg). All diabetic rats maintain blood glucose above 167mmol/L 25 rats served as controls. Six rats from each group were sacrificed at 1,2,4,8 weeks after estimated their body weight. The kidney hypertrophy index was representedby kidney weight/ body weight ratio. At each point interval ,the sera were collected for% measuring blood glucose ,C peptide , creatinine as well as urea .The spot urine wasobtained for determination of urinary albumin excretion rate .expressed as urinary albumin /creatinine ratio(A/C). Right kidney was fixed in 4% formal solution over night and paraffin-embedded for immunohistochemical examination( collagen IV and a SMA). Quantitative assessment of immunohistochemical staining was determined by FAnalyPpwer image analyzer.Statistical analysis. Results are expressed as mean and standard deviations(mean盨D) or median (range) .Data on A/C and a SMA were tested with Wilcoxon rank-sum test. Other results were compared using the two-sample Student's test or one-way analysis of variance. P<0.05 is taken as significant.Results:1. There was no difference in sex between two groups. Serum glucose, creatinine ,urea were increased(P<0.05) and serum C peptide was decreased(/)<0.05) in diabetic rats compared with those in controls. No significant change in A/C was found between diabetic rats and controls.2. In diabetic groups , there was a progressive increase in kidney weight with time(at 8 weeks. PO 05 ). Diabetic rats had a significant increase in kidney hypertrophy index compared with controls (PO.05).3. The detection of immunoreactive a SMA was confined to the vascular media innormal young rat kidneys . In diabetic rats, expression of a SMA in the renal interstitium was significantly higher than that in controls at all time-points, a SMA was also increased within diabetic mesangial cells before 2 weeks . Some tubular cells of diabetic rats showed immunostain for a SMA.4. Compared with controls , diabetic rats had an ealy and steady increased deposition of collagen IV in the interstitium and glomerular.5. Either in glumerlular or in interstitium , significant positive correlations were found between a SMA and collagen IV in diabetic rats (r=0.712, P=0.000; r=0.520, p=0.013, respectively). The expression of a SMA in diabetic interstitium was associated with blood glucose(r=0.754 , ?=0.000) ,kidney hypertrophy index(r=0.643, /M).000) , blood creatinine (r=0.628, /M).000) as well as urea O=0.507,Conclusions:1. The level of a SMA is increased in the interstitium and glomerular of STZ induced diabetic rats.2. The increase of a SMA is associated with the deposition of collagen IV in experimental diabetic nephropathy3. In STZ induced diabetic rats , activated myofibroblasts in the interstitium are associated with kidney hypertrophy and renal dysfun...