Regulation of bile acid synthesis in rat hepatocyte monolayer cultures
Primary hepatocyte monolayer cultures (PHC) were prepared and incubated in serum free media. Cells from a cholestyramine fed rat converted exogenous (/sup 14/C)-cholesterol into (/sup 14/C)-bile acids at a 3-fold greater rate than rats fed a normal diet. PHC synthesize bile acids (BA) at a rate of approximately 0.06 ..mu..g/mg protein/h. The major bile acid composition, as determined by GLC, was ..beta..-muricholic acid (BMC) and cholic acid (CA) in a 3:1 ratio, respectively. PHC rapidly converted free BA and BA intermediates into taurine conjugated trihydroxy-BA up to 87h after plating. 3-Hydroxy-3-methylglutaryl-coenzyme A-reductase activity assayed in microsomes prepared from PHC, decreased during the initial 48h, then remained constant. Cholesterol 7..cap alpha..-hydroxylase activity decreased during the initial 48h, then increased during the next 48h. This occurred while whole cells produced BA at a linear rate. The effect of individual BA on bile acid synthesis (BAS) was also studied. Relative rates of BAS were measured as the conversion of (/sup 14/C)-cholesterol into (/sup 14/C)-BA. BA combinations were tested in order to simulate the composition of the enterohepatic circulation. The addition of TCA (525 ..mu..M) plus TCDCA (80..mu..M), in concentrations which greatly exceed the concentration of BA (60..mu..M) in rate portal blood, failed to inhibit BAS. BA plus phospholipid and/or cholesterol also did not inhibit BAS. Surprisingly, crude rat bile with a final concentration comparable to those in the synthetic mix inhibited (/sup 14/C)-cholesterol conversion into (/sup 14/C)-BA.
- Research Organization:
- Virginia Associated Research Center, Blacksburg (USA)
- OSTI ID:
- 6792274
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
59 BASIC BIOLOGICAL SCIENCES
ANIMAL CELLS
BILE ACIDS
BIOSYNTHESIS
CARBON 14 COMPOUNDS
CARBOXYLIC ACIDS
CELL CULTURES
CHOLESTEROL
CHROMATOGRAPHY
ENZYME ACTIVITY
HYDROXY COMPOUNDS
LABELLED COMPOUNDS
LIQUID COLUMN CHROMATOGRAPHY
LIVER CELLS
ORGANIC ACIDS
ORGANIC COMPOUNDS
SEPARATION PROCESSES
SOMATIC CELLS
STEROIDS
STEROLS
SYNTHESIS