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Background. Long-term bile duct obstruction causes sinusoidal regurgitation of bile acids, a shift in bile acid metabolism, and alterations of liver histology. In this study we investigated the regurgitation of bile acids during short-term bile duct obstruction and its reversibility and reproducibility. In addition, the biotransformation of taurodeoxycholate and its appearance in bile and perfusate effluent were studied as well as liver histology.Methods. Rat livers (n = 5) were perfused in vitro with 32 nmol/min/g liver taurodeoxycholate over 85 min with the bile duct being intermittently closed for 30 and 20 min, respectively.Results. Within the first 5 min after bile duct obstruction bile acids started to regurgitate to the perfusate effluent amounting to ∼15% of hepatic uptake until the end of the perfusion period. After relief of obstruction, bile flow and biliary bile acid excretion showed an overshoot phenomenon and were almost doubled compared to preobstruction. In contrast, sinusoidal bile acid regurgitation declined. The same phenomenon was observed during the second closure/opening cycle of the bile duct. Regurgitated bile acids consisted of significantly more taurodeoxycholate metabolites (∼70%) than did biliary bile acids (∼30%). Histology of liver parenchyma was preserved.Conclusions. During repetitive short-term bile duct obstruction bile acid regurgitation is reversible and reproducible. The absence of altered mechanical barriers suggests that specific pathways are involved in the regurgitation process of bile acids. [Copyright &y& Elsevier]