Lipoprotein snthesis and secretion b cultured human intestinal mucosa

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Abstract
Cultured human jejunal mucosa was tested on whether it incorporates fatty acid into esterified lipids and whether organ culture can serve as a model system to study lipoprotein secretion by the human gut. Jejunal biopsies obtained from 7 subjects were cultured for 24 h in medium containing 2 .mu.Ci of [3H]palmitic acid. More than 95% of the radioactivity incorporated by the tissue was associated with esterified lipids: triglycerides, cholesterol esters and phospholipids, 7.8 .+-. 1.2, 0.5 .+-. 0.1 and 14.0 .+-. 1.5 nmol/10 mg weight, respectively. During the culture labeled triglycerides, phospholipids and cholesterol esters were secreted to the medium. Most of the newly synthesized esterified lipids in the medium were found in the d [density] < 1.019 g/ml and d = 1.019-1.063 g/ml fractions. The majority of the newly synthesized triglycerides were found in the d < 1.019 g/ml fraction. Labeled cholesterol esters were enriched in the d = 1.063-1.21 g/ml fraction. Boiled biopsies adsorbed negligible amounts of radioactive palmitic acid and did not synthesize esterified lipids. The addition of puromycin to the culture medium and preincubation with cholchicine resulted in decreased uptake of the labeled fatty acid and decreased secretion of esterified lipids to the medium. Cultured human intestinal mucosa is apparently a suitable model to study lipid synthesis and lipoprotein secretion by the human intestine.