Journal of Lipid Research, Vol 25, 437-447, Copyright © 1984 by Lipid Research, Inc.
The economy of the enterohepatic circulation of bile acids in the baboon. 2. Regulation of bile acid synthesis by enterohepatic circulation of bile acids
RN Redinger
Isotope dilution within bile acid pools and radiochemical assessment of
cholesterol oxidation to bile acids were methods used to measure short-
term feedback regulation of bile acid synthesis in baboons with controlled
enterohepatic circulations. Intraduodenal infusion of labeled endogenous
bile acid pools into bile acid-depleted animals with enhanced bile acid
synthesis showed that the rate of bile acid returned to the liver affected
the degree of inhibition of bile acid synthesis. Infusion of prepared bile
acid pools of varying composition resulted in a specific pattern of
feedback inhibition of bile salt synthesis related to pool composition and
mass. Individual bile salts inhibited their own synthesis more than that of
other bile salts, and chenodeoxycholic and deoxycholic acids were found to
have greater inhibitory effects than cholic acid. Glycine-conjugated cholic
and chenodeoxycholic acids had greater inhibitory effects than did the
respective free bile salts. Infusion of mixed bile acid pools showed that
dihydroxy bile acids (chenodeoxycholic or deoxycholic) enhanced feedback
inhibition of cholic acid. In all studies, inhibition of bile acid
synthesis occurred twice as fast as its derepression.
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