Objective To observe the impact of lisnopril on cytokines in peritoneum of rat peritoneal fibrotic model and study effect of lisnopril on peritoneal fibrosis and its potential mechanism.Methods Thirty-six male Sprague-Dawley rats were randomly divided into 3 groups (n=12 each):control group (NS group),in which the rats were treated with daily intraperitoneal injection of 0.9% NaCl 15 ml);model group (PDF group),in which the rats were treated with daily intraperitoneal injection of 4.25% saccharated dialysate 15 ml combined with injection of erythromycin lactobionate (6.25 ×104 U )at day 7,14,21 and 28;lisnopril treatment group (LIS group),in which 0.8 mg/100 g lisinopril capsule in gastric perfusion was added once a day besides the same intraperitoneal injecting as model group.All rats were sacrificed five weeks after intraperitoneal injection,and the parietal and visceral peritoneum were sampled.The vascular count and histologic changes were observed.The expression levels of transforming growth factor beta1(TGF-β1) and fibronectin (FN) were assayed by SP immunohistochemistry method.Results Compared with PDF group,the vascular count of peritoneum (mesenterium) obviously decreased [(4.17±1.11) vs (7.33±1.61)per visual field,P0.05] in LIS group.Peritoneal tissure markedly thickened,and infiltration of inflammatory cells and fibroid substance proliferation could be significantly found in PDF group,and these changes remarkably decreased in LIS group.Compared with PDF group,the expression rates of FN [(56.21±3.05)% vs (71.51±4.76)%,P0.05] and TGF-beta1 [(48.77±2.68)% vs (66.74±2.47)%,P0.05] obviously decreased in LIS group.Conclusions Lisnopril may suppress expression of TGF-β1,reduce extracellular matrix FN accumulation,improve peritoneal fibrosis and thereby play a role of protecting peritoneum.