Spironolactone, Enalapril And Their Combination Ameliorates Renal Interstitial Fibrosis In Rat With Complete Unilateral Ureteral Obstruction

Objective: To investigate whether spironolactone, a mineralocorticoid receptor antagonist, alone or in combination with enalapril, an angiotensin converting enzyme inhibitor (ACEI), ameliorates renal interstitial fibrosis in an experimental model of complete unilateral ureteral obstruction (UUO).Methods: Thirty male SD rats were randomly assigned to five groups and were treated as follows: sham operation group (sham group), UUO group, spironolactone treatment group (50mg.k^-1.d^-1), enalapril treatment group (31mg.k^-1.d^-1) and their combination group. Immunohistochemistry were performed to examine the expression of transforming growth factor beta 1(TGF-β₁) and fibronectin (FN) at the 14^th day in the kidney. The expression areas of TGF-β₁ and FN were quantitatively analyzed by image analysis. HE and Masson Trichrome staining were performed to investigate renal pathological changes and the degree of interstitial fibrosis. The fibrotic areas were also quantitatively analyzed by image analysis. The expression of collagen type I were measured by Western blot. The plasma concentration of sodium, potassium, creatinine and blood urea nitrogen was detected at the 14^th day after UUO.Results: In comparison with the sham group, the area of TGF-β₁ and FN deposition increased significantly in UUO group and three treatment groups (P<0.05). The area of TGF-β₁ and FN deposition in three treatment groups were apparently less than those in UUO group(P<0.05). The expression of TGF-β₁ in combination treatment group was significantly reduced compared with spironolactone treatment group (P<0.05) and elanapril treatment group (P<0.05). There were no statistically significant difference between spironolactone treatment group and elanapril treatment group (P>0.05). The expression of TGF-β₁ in tubules and interstitium was closely related to the expression of FN (r =0.893, P<0.05) and the fibrotic areas (r=0.787, P<0.05).The expression of FN was also closely related to the fibrotic areas (r=0.805, P<0.05). Western blot showed that in comparison with the sham group, the expression of collagen type I (Col I ) protein in UUO group and treatment groups were significantly upregulated (P<0.05), Compared with UUO group, collagen type I protein were downregulated in treatment groups especially in combination treatment group (P<0.01). There were no statistically significant difference between spironolactone treatment group and elanapril treatment group (P>0.05). Compared with UUO group, the plasma concentration of potassium in combination treatment group was significantly increased (P<0.05). Compared with sham group, the plasma concentration of sodium in combination treatment group was significantly decreased (P<0.05). The plasma concentration of creatinine and blood urea nitrogen was significantly increased in UUO group (P<0.05) and in combination treatment group (P<0.05).Conclusions:1. UUO is a ripe, well-characterized model of experimental renal disease culminating in tubulointerstitial fibrosis.2. The increase of FN and Col I were correlated with the increased expression of TGF-β₁ and the degree of interstitial lesions in obstructive nephropathy.3. Spironolactone may suppress fibrosis, at least in part via down-regulating TGF-β₁ expression and decrease accumulation of extracellular matrix include FN and Col I . Its anti-fibrosis effect may be similar to ACE inhibitor.4. concomitant use of spironolactone and ACE inhibitor had synergistic effect on extenuating tubulointerstitial fibrosis5. concomitant use of spironolactone and ACE inhibitor also added the risk of the upregulation of the plasma concentration of potassium and renal hypofunction, thus we should monitor plasma concentration of electrolytes and renal function.