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Complex feedback regulation of bile acid synthesis in the hamster: The role of newly synthesized cholesterol
Author(s) -
Scheibner Jürgen,
Fuchs Michael,
Hörmann Erwin,
Stange Eduard F.
Publication year - 1999
Publication title -
hepatology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.488
H-Index - 361
eISSN - 1527-3350
pISSN - 0270-9139
DOI - 10.1002/hep.510300135
Subject(s) - hamster , cholesterol synthesis , bile acid , cholesterol , chemistry , biochemistry , medicine , reductase , enzyme
Hepatic bile acid synthesis is regulated by recirculating bile acids, possibly by modulating the availability of newly synthesized and preformed cholesterol. Because data in the hamster on this mechanism are lacking, we fitted these animals with an extracorporeal bile duct and administered tritiated water intraperitoneally to label newly formed cholesterol. After interruption of the enterohepatic circulation, physiological and double‐physiological doses of conjugated cholate (25 or 50 μmol/100 g · h) or of unconjugated deoxycholate (6 or 12 μmol) were infused intraduodenally for 54 hours and compared with controls. De novo and preformed cholesterol directly secreted into bile or used for cholate and chenodeoxycholate synthesis were quantitated by high‐pressure liquid chromatography (HPLC)‐liquid scintillation. Directly after depletion of the bile acid pool (6‐9 hours) at nearly physiological conditions, chenodeoxycholate synthesis was significantly reduced by cholate and deoxycholate by up to 45% to 51%, whereas cholate formation decreased by ≈22% during deoxycholate. This short‐term effect was mainly mediated by reduced synthesis from preformed cholesterol. After long‐term bile depletion (30‐54 hours), bile acid synthesis returned to control levels during 25 μmol of cholate and of both deoxycholate doses. In contrast, only 50 μmol of cholate prevented derepression of bile acid synthesis. This long‐term effect was mainly attributed to a diminished formation from de novo cholesterol exceeding the reduced synthesis from preformed cholesterol. In summary, short‐ and long‐term regulation of bile acid synthesis in hamsters differs with respect to availabilities of preformed and de novo cholesterol.