| Objective It is well known that TGF- β1 is a key cytokine in pancreatic fibrosis, but there is little knowledge about wheather the expression of its two receptors T β RI and T β RII change. We made chronic pancreatitis in male Wistar rats in order to evaluate the expression of TGF- β1 and its receptors in the process of pancreatic fibrosis. Furthermore, to study the pathogenesis of chronic pancreatitis.Methods 48 male Wistar rats were put into 2 groups: control group and model group, each group had 24 rats. Model group rats received intraperitoneal injection of 750mg/kg BW of DDC twice a week. Control group rats received intraperitoneal injection of 7.5ml/kg BW of saline solution twice a week. From the end of the first week, 4 rats of each group were killed. Some of the pancreatic fragments were immediately fixed in 10% buffered formalin, processed for paraffin-embedded sectioning, and stained with hematoxylin and eosin. The results of microscopic findings were scored by the pathologist with expertise in pancreatic pathology who was blinded to which experimental procedures were performed on the specimen under observation. Findings of acinar cell atrophy, fibrosis (intralobular or interlobular), and inflammatory cell infiltration were evaluated according to the following scoringsystem: 0= absent, 1= a lesion slightly shown in the lobule or intralobular region (less than one half), 2= a lesion widely shown in the lobule or intralobular region (more than one half), and 3= a lesion shown across lobules and intralobular regions or with destruction of lobular architecture). The score of each section was determined according to the total scores of the lesions in three randomly selected low-power microscopic fields of each section obtained from two portions of the pancreas. Other pancreatic framents were put in Eppendorf tube and saved in -80 ℃ refragerator, then RT-PCR were employed to test the expression of TGF- β 1 and itsI and II receptors. Liver and kidney were also excided, fixed in 10% buffered formalin, processed for paraffin-embedded sectioning, and stained with hematoxylin and eosin for microscopic observation.Each value was expressed as the mean±SD. Statistical analysis was performed using the Statistical Package of the SPSS 11.0. Continuous variables were tested by analysis of t-test and the relations between the variables were tested by linear correlation. P<0.05 was considered to be a significant difference.Results ①In the first 3 weeks, model group rats grew slowly in contrast to control group. From the 4th week, rats in model group began to lose weight, there was a significant difference between the weight of the two groups.②Fibrosis appeared from the second week in model group rats'pancreas, while there was little change in control group's. The difference was significant.③The expression of TGF-β1 and its I and II receptors was significantly higher than that of the control group. ④ TGF- β 1 and its I and II receptor each has a correlation with the extent of pancteatic fibrosis, the correlation coefficient was 0.87, 0.93, 0.92 respectively.Conclusions①It takes a few weeks to create an animal model of chronic pancreatitis by intraperitoneal injection of 750mg/kg BW of DDC to male Wistar rats twice a week. ②In the process of pancreatic fibrosis, the expression of TGF- β 1 and its I and II receptor increase gradually. ③ TGF- β 1 and its I and II receptor play an important role in the process of pancreatic fibrosis.
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