Apolipoprotein B synthesis in rat small intestine: regulation by dietary triglyceride and biliary lipid
Apolipoprotein B (apoB) synthesis rates have been determined, in vivo, in rat enterocytes. Following intralumenal administration of a pulse of (/sup 3/H)leucine, newly synthesized apoB was quantitated by specific immunoprecipitation and compared to (/sup 3/H)leucine incorporation into total, trichloroacetic acid-insoluble protein. ApoB synthesis rates were determined after acute administration of either 0.1 or 1 g of triglyceride to fasting animals. No differences were found at any time from 90 min to 6 hr after challenge and values were not different from the basal values established in fasted controls. Animals rechallenged with triglyceride after 8 days' intake of fat-free chow also failed to demonstrate a change in intestinal apoB synthesis rate. By contrast, enterocyte content of apoB appeared to fall, temporarily, with the onset of active triglyceride flux. Groups of animals were then subjected to external bile diversion for 48 hr, a maneuver designed to remove all lumenal sources of lipid. Jejunal apoB synthesis rates fell by 43% (from 0.76% +/- 0.14 to 0.43% +/- 0.12, P less than 0.001), a change that was completely prevented by continuous replacement with 10 mM Na taurocholate. The suppression of jejunal apoB synthesis, induced by prolonged bile diversion, was reversed after 14 hr, but not 8 hr, of intralumenal perfusion with 10 mM Na taurocholate. The addition of micellar fatty acid-monoolein to the perfusate for 4 hr produced no further change in apoB synthesis. Ileal apoB synthesis rates fell by 70% (from 0.61% +/- 0.15 to 0.18% +/- 0.10, P less than 0.001) following 48 hr external bile diversion, a change that was only partially prevented by continuous bile salt replacement. These results suggest that jejunal apoB synthesis demonstrates bile salt dependence but not regulation by acute triglyceride flux.
- Research Organization:
- Columbia Univ., New York, NY
- OSTI ID:
- 5810007
- Journal Information:
- J. Lipid Res.; (United States), Vol. 1
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
APOLIPOPROTEINS
BIOSYNTHESIS
BILE
BIOCHEMICAL REACTION KINETICS
CARBOXYLIC ACIDS
IN VIVO
LEUCINE
LIPIDS
RADIOIMMUNOASSAY
RATS
SMALL INTESTINE
TRACER TECHNIQUES
TRIGLYCERIDES
TRITIUM COMPOUNDS
AMINO ACIDS
ANIMALS
BIOLOGICAL MATERIALS
BODY
BODY FLUIDS
DIGESTIVE SYSTEM
ESTERS
GASTROINTESTINAL TRACT
IMMUNOASSAY
IMMUNOLOGY
INTESTINES
ISOTOPE APPLICATIONS
KINETICS
LABELLED COMPOUNDS
LIPOPROTEINS
MAMMALS
MATERIALS
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANS
PROTEINS
RADIOASSAY
RADIOIMMUNOLOGY
REACTION KINETICS
RODENTS
SYNTHESIS
VERTEBRATES
550201* - Biochemistry- Tracer Techniques