Enterohepatic circulation in the rat

Several compounds, in particular bile acids, undergo enterohepatic circulation (EHC). Limited data are available on the pathophysiologic aspects of this circulation. In the present study we describe a surgical technique in rats that allows a long-term, reversible interruption of the EHC and monitoring of peripheral blood levels without direct surgical intervention. This technique excludes the effects of anesthesia and surgical trauma. The model's validity has been tested extensively. We used this animal model to investigate acute and chronic effects of interruption and subsequent restoration of the EHC on (a) nutritional status, (b) plasma cholesterol levels and hepatic cholesterol synthesis, and (c) biliary bile acid, phospholipid, and cholesterol excretion. Interruption of the EHC resulted in an increased food intake and enhanced fecal energy loss, caused by a less efficient intestinal absorption. Plasma cholesterol concentrations declined immediately after the interruption of the EHC, but returned to almost control values during bile diversion. A marked overshoot followed the subsequent restoration of the EHC. Hepatic cholesterol synthesis showed a five-fold increase after 8 days of bile diversion but returned to control values within 2 days after restoration of the EHC. After interruption of the EHC, bile acid, phospholipid, and cholesterol excretion decreased sharply but stabilized after 3 h at 7.6%, 20%, and 23%, respectively, of their initial values. Bile acid output, representing hepatic synthesis, slowly increased over 4 days, but never exceeded 13% of its value during intact EHC. Subsequent restoration of the EHC could rapidly reverse the observed effects of the interruption. The animal model described in the present study is an excellent tool in studying the acute and chronic effects of disturbances of the EHC.