Synthesis and release of lipids and lipoproteins by isolated rat jejunal enterocytes in the presence of sodium taurocholate.
Isolated rat jejunal villus and crypt cells prepared by differential scraping and hyaluronidase dispersion were used in the presence of 8 mM sodium taurocholate to study the incorporation of sn-[3H]glycerol-2-monooleate, [1-14C]palmitate, [1-14C]acetate, L-[4,5(n)-3H]leucine and D-[1-14C]glucosamine into cellular and medium lipids and proteins, respectively. The villus cells were capable of an apparently normal biosynthesis of triacylglycerols and phospholipids, as well as of proteins and glycoproteins despite an altered dye permeability and increased release of cytosolic and membrane enzymes. About 20-30% of the newly formed triacylglycerols and about 35% of the newly formed phospholipids were secreted into the medium and were recovered as triacylglycerol-rich particles. Labelled proteins and glycoproteins were also recovered from this fraction. The crypt cells synthesized about one-half as much triacylglycerol and phospholipid as did the villus cells, but secreted little or no labelled lipid into the postincubation medium. The release into the medium of triacylglycerols synthesized by the villus cells was blocked by a pretreatment of the isolated cells with the microtubule disruptors, nocodazole, colchicine and colcemid; by the amino sugar, D-galactosamine; by the inhibitors of protein synthesis, puromycin and cycloheximide, and by the inhibitor of the biosynthesis of phosphatidylcholine, chlorocholine. These results indicate that the secretion of labelled lipids, proteins and glycoproteins by the upper villus enterocytes in the presence of sodium taurocholate is not entirely due to cell breakage and spillage of contents. It is concluded that incubations of isolated villus cells of rat jejunum with mixed micellar solutions containing 8 mM taurocholate are compatible with an apparently normal biosynthesis and secretion of triacylglycerol-rich particles.
D000469:Alkaline Phosphatase / Q000378:metabolism; D000818:Animals; D007583:Jejunum / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D007700:Kinetics; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D050356:Lipid Metabolism; D008055:Lipids / Q000096:biosynthesis; D008074:Lipoproteins / Q000096:biosynthesis / Q000378:metabolism*; D008297:Male; D008823:Micelles; D051381:Rats; D013656:Taurocholic Acid / Q000378:metabolism / Q000494:pharmacology*; D014280:Triglycerides / Q000378:metabolism
D008055:Lipids; D008074:Lipoproteins; D008823:Micelles; D014280:Triglycerides; D013656:Taurocholic Acid; D007770:L-Lactate Dehydrogenase; D000469:Alkaline Phosphatase